Also, app.installedApk.sig is set in App.initInstalledApk()
from 3a5ecc5e8ec6c820dbfdb788dc06f7dbb0699c18
refs #1305
refs #855
java.lang.NullPointerException
at org.fdroid.fdroid.data.App.getInstance(App.java:390)
at org.fdroid.fdroid.localrepo.CacheSwapAppsService.onHandleIntent(CacheSwapAppsService.java:77)
at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.os.HandlerThread.run(HandlerThread.java:60)
6bcc1f2e68