Settings: Fix isPackageInstalled logic.

    - If package is null, isPackageInstalled returned true.
    - Return false if null, always.
    - PS2: Fix codestyle
Change-Id: If2bf41e4c9520195d56e327a447d7085daab3154
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_packages_apps_Settings into android-4.4