For some odd reason, something is sending a URL to be downloaded that then
results in a null Apk instance. My first guess was because it was being
canceled, but the interrupted receiver is not even registered yet. My
second thought is that something is sending a download and cancel Intent at
the same time. In any case, its something to keep in mind when reworking
InstallManagerService once InstallerService comes along.
closes#660https://gitlab.com/fdroid/fdroidclient/issues/660
c862eb0bd3