Fix: Custom lockscreen force close

https://paranoidandroid.atlassian.net/browse/AOSPA-140

Attempting to create a blurred image on first run causes a force close
if an image wasn't first selected. Have the user crop the current wallpaper
for use in such cases.

Change-Id: I272316b837ef2c9595ef09095efcb6ff9ae3255d
Merge "Fix: Custom lockscreen force close" into kitkat