redfam: Check if moved page exists

To prevent creation of orphaned diskpages in case of special movement
constructs

Issue #71 (#71)

lib/redfam.py

@@ -598,6 +598,11 @@ class RedFamWorker( RedFam ):
             if self.article_has_status( "redirect", title=article ):
                 try:
                     page = page.moved_target()
+
+                    # Short circuit if movement destination does not exists
+                    if not page.exists():
+                        continue
+
                 except pywikibot.exceptions.NoMoveTarget:
                     pass