Yet another demo: https://drive.google.com/file/d/0B0nwzlfiB4aQVmEtbW4zMXM1NU0/edit?usp=sharing

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/meld/meldwindow.py", line 558, in <lambda>
    lambda b: self.try_remove_page(page))
  File "/usr/lib/python2.7/site-packages/meld/meldwindow.py", line 526, in try_remove_page
    response = page.on_delete_event(appquit)
  File "/usr/lib/python2.7/site-packages/meld/filediff.py", line 895, in on_delete_event
    response = self.check_save_modified()
  File "/usr/lib/python2.7/site-packages/meld/filediff.py", line 888, in check_save_modified
    if not self.save_file(i):
  File "/usr/lib/python2.7/site-packages/meld/filediff.py", line 1651, in save_file
    extrabuttons=[ buttons[b] for b in bufdata.newlines ] )
  File "/usr/lib/python2.7/site-packages/meld/misc.py", line 83, in run_dialog
    d.image.set_alignment(0.5, 0)
AttributeError: 'MessageDialog' object has no attribute 'image'

Can you check if this issue is still present for you with the latest updates for Meld?

Reproducted this issue in mercurial with meld on centos 7  system.

This message is a reminder that Fedora 20 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 20. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
this bug will be closed as EOL if it remains open with a Fedora  'version'
of '20'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not 
able to fix it before Fedora 20 is end of life. If you would still like 
to see this bug fixed and are able to reproduce it against a later version 
of Fedora, you are encouraged  change the 'version' to a later Fedora 
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events. Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.

No do NOT delete it.
As described above, the bug also occurs on CentOS 7 so EOL is not applicable, could the assignee please change over these details so the bug is not incorrectly deleted.

On my system (also CentOS 7) I believe the bug occurs as a result of a dialogue window due to mixed line endings ocurring in the file (which explains why I notice it intermittently)

The crash itself is the identical error as Mikhael gets (misc.py:83).

My version is meld-3.11.0-1.el7.2

There shortly will be an update to Meld 3.13.1 available:

http://koji.fedoraproject.org/koji/buildinfo?buildID=640746

Can you test if this fixes the issue for you?

Thanks & Regards,
Dominic