CM11 Themes: Ensure customTheme is not null.

The configuration retrieved via getConfiguration() sometimes contains
a null customTheme which results in the theme returning to holo when
applying a component such as icons.  Icons will change but styles
and fonts would return to the default.

Change-Id: Iac0cb8eed5de8fdc9fe8efd697d968f26e801c08
Merge "CM11 Themes: Ensure customTheme is not null." into cm-11.0
Merge branch 'upstream/cm-11.0'