Fix ArchQuery.rpmvercmp if one of its arguments is None

The None argument is always <= than the other argument. We need this
in case of a broken/pathological package where version() or release()
return None (see vercmp (which calls rpmvercmp)).

osc/util/archquery.py

@@ -137,6 +137,10 @@ class ArchQuery(packagequery.PackageQuery, packagequery.PackageQueryResult):
         """
         if ver1 == ver2:
             return 0
+        elif ver1 is None:
+            return -1
+        elif ver2 is None:
+            return 1
         res = 0
         while res == 0:
             # remove all leading non alphanumeric chars