This mv has no destination. Check the arguments.

Problematic code:

mv "$file $dir"

Correct code:

mv "$file" "$dir"

Rationale:

ShellCheck found an mv command with a single parameter. This may be because the source and destination was accidentally merged into a single argument, or because the line was broken in an invalid way.

Fix the mv statement by correctly specifying both source and destination.

Exceptions:

None