When generating the report, summed changes need to be non-empty (#132).

Previoulsy, we were just checking against the changes returned from the
last repository analyzed - which of course broke the whole thing if that
repository had no matching commits!

gitinspector/gitinspector.py

@@ -82,7 +82,7 @@ class Runner(object):
 		format.output_header(repos)
 		outputable.output(ChangesOutput(summed_changes))
 
-		if changes.get_commits():
+		if summed_changes.get_commits():
 			outputable.output(BlameOutput(summed_changes, summed_blames))
 
 			if self.timeline: