GUI needs validations

[xeon-zolt]

when using GUI button to select gif it and

• I select an image it sets that as wallpaper which should not be the case I suppose

• or when I select a deb file (crazy) it does nothing and in the terminal, I have a warning Failed to recognize the file format.

• works well for both videos (still should not) and gifs but GUI just doesn't know what to do as it goes blank I think it should close and fork the command check below ss for understanding this
  after and before situations
  
  

[gabru-md]

@xeon-zolt I will look into this issue for the time being.
I will probably try to solve it and send a PR for the same :)