App allowed me to upload duplicates

[nicolas-raoul]

1. I took 50 pictures of a temple.
2. First, I uploaded 20 of them (custom picker).
3. Then, I uploaded 20 without really checking carefully (custom picker but icon not shown probably due to this other bug). Probably I mistakenly selected the same pictures
4. The app, in the metadata entry screens, is supposed to check whether the picture already exists on the server, but I did not receive any such notification.
5. Now there are many duplicates on the server. Example: https://commons.wikimedia.org/wiki/File:%E9%9B%AA%E3%83%B6%E8%B0%B7%E5%85%AB%E5%B9%A1%E7%A5%9E%E7%A4%BE_(23792).jpg = https://commons.wikimedia.org/wiki/File:%E9%9B%AA%E3%83%B6%E8%B0%B7%E5%85%AB%E5%B9%A1%E7%A5%9E%E7%A4%BE_(24203).jpg

I just tried again now with the system picker for that same picture, and the app correctly tells me Image is already on Commons:

[sonalyadav1]

@nicolas-raoul working on this issue.