It took a couple of day for it to happen again, but here's the human readable backtrace:
Jan 08 13:01:55 deech-thinkpad systemd-coredump[25660]: Process 27577 (emacs) of user 1000 dumped core.

                                                        Stack trace of thread 27577:
                                                        #0  0x00007efc14652f5f raise (libpthread.so.0)
                                                        #1  0x00000000004e33b1 terminate_due_to_signal (emacs-25.1)
                                                        #2  0x00000000004fa83e handle_fatal_signal (emacs-25.1)
                                                        #3  0x00000000004faa43 deliver_thread_signal (emacs-25.1)
                                                        #4  0x00000000004faaaf deliver_fatal_thread_signal (emacs-25.1)
                                                        #5  0x00007efc14653080 __restore_rt (libpthread.so.0)
                                                        #6  0x00000000004a9fa0 turn_on_face (emacs-25.1)
                                                        #7  0x00000000004ae0f2 tty_write_glyphs (emacs-25.1)
                                                        #8  0x000000000041904a update_frame_line (emacs-25.1)
                                                        #9  0x000000000041c866 update_frame_1 (emacs-25.1)
                                                        #10 0x000000000041e08e update_frame (emacs-25.1)
                                                        #11 0x0000000000450cd4 redisplay_internal (emacs-25.1)
                                                        #12 0x00000000004ed1db read_char (emacs-25.1)
                                                        #13 0x00000000004efba0 read_key_sequence (emacs-25.1)
                                                        #14 0x00000000004f16c6 command_loop_1 (emacs-25.1)
                                                        #15 0x0000000000552c32 internal_condition_case (emacs-25.1)
                                                        #16 0x00000000004e37ec command_loop_2 (emacs-25.1)
                                                        #17 0x0000000000552bd3 internal_catch (emacs-25.1)
                                                        #18 0x00000000004e3750 command_loop (emacs-25.1)
                                                        #19 0x00000000004e7d77 recursive_edit_1 (emacs-25.1)
                                                        #20 0x000000000050ef5f read_minibuf (emacs-25.1)
                                                        #21 0x000000000050f6df Fread_from_minibuffer (emacs-25.1)
                                                        #22 0x00000000005543c0 Ffuncall (emacs-25.1)
                                                        #23 0x000000000058a32b exec_byte_code (emacs-25.1)
                                                        #24 0x000000000055426b Ffuncall (emacs-25.1)
                                                        #25 0x000000000058a32b exec_byte_code (emacs-25.1)
                                                        #26 0x000000000055426b Ffuncall (emacs-25.1)
                                                        #27 0x00000000005555c8 Fapply (emacs-25.1)
                                                        #28 0x0000000000554351 Ffuncall (emacs-25.1)
                                                        #29 0x000000000058a32b exec_byte_code (emacs-25.1)
                                                        #30 0x000000000055426b Ffuncall (emacs-25.1)
                                                        #31 0x00000000005555c8 Fapply (emacs-25.1)
                                                        #32 0x0000000000554351 Ffuncall (emacs-25.1)
                                                        #33 0x000000000058a32b exec_byte_code (emacs-25.1)
                                                        #34 0x000000000055426b Ffuncall (emacs-25.1)
                                                        #35 0x000000000058a32b exec_byte_code (emacs-25.1)
                                                        #36 0x0000000000553358 apply_lambda (emacs-25.1)
                                                        #37 0x000000000055366f eval_sub (emacs-25.1)
                                                        #38 0x00000000005564cd Fprogn (emacs-25.1)
                                                        #39 0x0000000000553841 eval_sub (emacs-25.1)
                                                        #40 0x0000000000553fed Fprogn (emacs-25.1)
                                                        #41 0x000000000055426b Ffuncall (emacs-25.1)
                                                        #42 0x000000000055019a Ffuncall_interactively (emacs-25.1)
                                                        #43 0x0000000000554351 Ffuncall (emacs-25.1)
                                                        #44 0x0000000000550b07 Fcall_interactively (emacs-25.1)
                                                        #45 0x000000000055442a Ffuncall (emacs-25.1)
                                                        #46 0x000000000058a32b exec_byte_code (emacs-25.1)
                                                        #47 0x000000000055426b Ffuncall (emacs-25.1)
                                                        #48 0x000000000055452a call1 (emacs-25.1)
                                                        #49 0x00000000004f18c1 command_loop_1 (emacs-25.1)
                                                        #50 0x0000000000552c32 internal_condition_case (emacs-25.1)
                                                        #51 0x00000000004e37ec command_loop_2 (emacs-25.1)
                                                        #52 0x0000000000552bd3 internal_catch (emacs-25.1)
                                                        #53 0x00000000004e37a9 command_loop (emacs-25.1)
                                                        #54 0x00000000004e7d77 recursive_edit_1 (emacs-25.1)
                                                        #55 0x00000000004e80b8 Frecursive_edit (emacs-25.1)
                                                        #56 0x0000000000414fee main (emacs-25.1)
                                                        #57 0x00007efc13e92291 __libc_start_main (libc.so.6)
                                                        #58 0x0000000000415b5a _start (emacs-25.1)

                                                        Stack trace of thread 27578:
                                                        #0  0x00007efc13f5148d poll (libc.so.6)
                                                        #1  0x00007efc17f6b786 n/a (libglib-2.0.so.0)
                                                        #2  0x00007efc17f6b89c g_main_context_iteration (libglib-2.0.so.0)
                                                        #3  0x00007efc17f6b8e1 n/a (libglib-2.0.so.0)
                                                        #4  0x00007efc17f930d5 n/a (libglib-2.0.so.0)
                                                        #5  0x00007efc14649454 start_thread (libpthread.so.0)
                                                        #6  0x00007efc13f5a7df __clone (libc.so.6)