Change text on missing wallpaper wallpaper

[Armin2208]

Off-topic: text like "...check if you <did something wrong>" can feel like you're blaming the user. Might be an idea to use something even more neutral, like "check if the file exists / is moved" for example.

Originally posted by @Jay-o-Way in #1144 (comment)

[Spiritreader]

But we are blaming the user! :D
If the wallpaper path is invalid, that's not on us,

My suggestion would be:

"Please verify that the file path is correct"