do not crash if no versionCode is found while parsing
do not crash if no versionCode is found while parsing

if vercode is None and max_vercode is None, then it gave None as an arg to
the regexp pattern in ignoresearch().

closes #261

f-droid/fdroid-server,f-droid/fdroid-server,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver