pm: Prevent a system_server crash is package name is null

 * If an app is placed on the system partition and it doesn't specify a
   valid package name, system_server will crash forever. Just skip it.

Change-Id: I9b911d40b3c4d7cf6fac8cc0166a2ba359329b7b
Merge "pm: Prevent a system_server crash is package name is null" into kk4.4