Prevent unhandled exception in NinePatchDrawable

Added null check in computeBitmapSize() to avoid unhandled
exception "java.lang.NullPointerException" at
android.graphics.Rect.<init>(Rect.java:72).

This problem was discovered in the wild.

Change-Id: I8a4729ceadcfc9744f11b8ceafdf24d6de88c645
1 file changed