Fix adding lockscreen targets.

The empty targets were not included in the setting properly.
Also make the code a little more memory efficient.

Change-Id: I05cc7ce55ef5789f063033116ebfd9337e5ee28a
Merge "Fix adding lockscreen targets." into cm-10.2
Merge branch 'cm-10.2' of https://github.com/CyanogenMod/android_packages_apps_Settings into cm-10.2

Conflicts:
	src/com/android/settings/cyanogenmod/LockscreenTargets.java

Change-Id: I61aed09539734f226689f1794c2d43cee5fd6075