Fix QFile::copy warning when the colors file doesn't exist
Summary:
There is no need to even look for a "Default.colors" file when
using the default color scheme, so skip the entire file copying
in that case.
Test Plan:
Just checked that the warning went away, I didn't test
the kde4 interaction.
Reviewers: mart, davidedmundson
Reviewed By: davidedmundson
Subscribers: plasma-devel, Plasma
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D8266