Fix NPE if themeContext is null - round 2

If a theme is uninstalled and timing is perfect, it can happen
that the CopyImageService is trying to get the PackageContext
of a not existing package.

Return from the function if a NameNotFoundException is catched.

Change-Id: I8f4e33d527f78228f9681ac518292364e9269a0c
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>
(cherry picked from commit d43dc8d6f5b80c1001d98bfe301309c0da9031f3)