Revert "Added a check for an selected image when toggling the editor"

This reverts commit 07d0aa4c7e0b5622ed434a29ec1f863b9fb6d4c4.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 621191 as the
culprit for flakes in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/flake/flake-culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vMDdkMGFhNGM3ZTBiNTYyMmVkNDM0YTI5ZWMxZjg2M2I5ZmI2ZDRjNAw

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.chromiumos/linux-chromeos-rel/18392

Sample Failed Step: non_single_process_mash_browser_tests

Sample Flaky Test: GalleryBrowserTest.DeleteImageWhileEditingOnDrive

Original change's description:
> Added a check for an selected image when toggling the editor
> 
> This provides a non-null check for the assert call.  When the assert
> call was being invoked with a null value, the edit mode was not being
> toggled.  Adding this in should allow deleting a single image to toggle
> the edit mode to off.
> 
> Bug: 912489
> Change-Id: I88cfa830d9780a5f1da94710939d4243f231aa2b
> Reviewed-on: https://chromium-review.googlesource.com/c/1388812
> Reviewed-by: Noel Gordon <noel@chromium.org>
> Commit-Queue: Alexander Nohe <nohe@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#621191}

Change-Id: I232da9107f44addfa135131b0010cc2f68edf4f2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 912489, 920299
Reviewed-on: https://chromium-review.googlesource.com/c/1403352
Cr-Commit-Position: refs/heads/master@{#621243}
3 files changed