Bug: org-capture-templates issues

[Haider Rizvi <harizvi@gmail.com>]

I'm getting the following error, when trying to do an org-capture. 

Debugger entered--Lisp error: (error "Invalid file location: nil")
  signal(error ("Invalid file location: nil"))
  error("Invalid file location: %S" nil)
  org-capture-expand-file((concat org-directory "inbox-gtd.org"))
  org-capture-target-buffer((concat org-directory "inbox-gtd.org"))
  org-capture-set-target-location()
  org-capture(nil)

My org-capture-templates is set as follows for ages: 
(setq org-capture-templates
      '(("t" "Todo" entry (file+headline  (concat org-directory "inbox-gtd.org") "Tasks")
         "* TODO %?\n  %i\n  %a")
         ))

org-directory: "/Users/hrizvi/Google Drive/MyDocs/org/"

With a fully qualified file-name, it works fine:

(setq org-capture-templates
      '(("t" "Todo" entry (file+headline  "/Users/hrizvi/Google Drive/MyDocs/org/inbox-gtd.org" "Tasks")
         "* TODO %?\n  %i\n  %a")
         ))

Reading up org-capture-expand-file, it seems org-directory is
prepended automatically, but it used to work fine in the
past. Flipping back to the older code for org-capture-expand-file
works fine. So I'd say this is a bug!

(emacs-version)
"GNU Emacs 26.0.50 (build 1, x86_64-apple-darwin16.7.0, NS appkit-1504.83 Version 10.12.6 (Build 16G29))
 of 2017-09-13"

(org-version)
"9.1.2"

org is installed from melpa-stable. From packages info: 
org is an installed package.

     Status: Installed in ‘org-20171004/’,
             shadowing a built-in package (unsigned).
    Version: 20171004
    Summary: Outline-based notes management and organizer
Required by: elfeed-org-20170423.128
Other versions: 20171004 (org), 20171002 (gnu), builtin.


-- Haider