(line-move-to-column) has a loop that can become infinite:

  (while (and ...)
    (goto-char (previous-char-property-change (point) line-beg)))

If (= (point) line-beg) then the (goto-char) does nothing, and the
condition in the while never changes. This patch adds a check to break
out of the while when this happens:

  (while (and ... (/= (point) line-beg))
    (goto-char (previous-char-property-change (point) line-beg)))

I'm seeing this in the wild with ERC and erc-fill-mode disabled. Simply
moving around an ERC buffer can hit this.