[Core][Preview image]: It should pop up Error opening file dialog if click the image which is deleted from OS.

[julieyuan]

Updating description because the scenario overlaps with #5978.
Steps:

1. Launch Brackets and open the default sample folder.
2. open index.html
3. switch to finder/explorer and delete screenshots/quick-edit.png from project
4. Back to Brackets and click this image quick-edit.png.
   Expected Result:
   At step 4, it doesn't pop up Error opening file dialog, but empty ImageViewer is displayed

ENV: MAC 10.8 and Win8.1 English OS

----------- original description:
Steps:

1. Launch Brackets and open the default sample folder.
2. Right click on the image quick-edit.png and select "Show in OS".
3. Delete this image from OS.
4. Back to Brackets and click this image quick-edit.png.
5. Try to rename or delete this image from Brackets by right clicking menu.

Results:
At step 4, it doesn't pop up Error opening file dialog.
At step5, it will pop up Error renaming file and Error deleting file dialog. (correct behavior)

Expected:
At step4, it should pop up Error opening file dialog to update the change outside of Brackets.

ENV: MAC 10.8 and Win8.1 English OS
Build: 0.33.0-10155

Snapshots:
Please refer to snapshot for details:

[peterflynn]

@julieyuan We don't update the tree when a text file is deleted externally only. It sounds like the only bug specific to Image Preview is that we don't show an error popup in step 4 when you click the deleted file?

[julieyuan]

@peterflynn yes, you are right. Sorry for the confusion. Correct the title to "It should pop up Error opening file dialog if click the image which is deleted from OS" (original is "The project tree is not update if the image is deleted from OS.")

[RaymondLim]

Nominating for sprint 34.

[njx]

Assigning to @couzteau

[peterflynn]

I bet we could fix this with a simple file.exists() check...

[couzteau]

Pull request with fix will follow as soon as the file system branch has been merged: #5797

The fix depends on file.exists API provided by new file system

[RaymondLim]

FBNC to @julieyuan

[julieyuan]

Thanks you all. The fix has not merged into latest build (0.34.0-10678, master fd686b4) yet. Will verify it with next build.