refactor: use null instead of vspace

src/beamerinnerthememoloch.dtx

@@ -117,7 +117,7 @@
     \ifx\insertinstitute\@empty\else\usebeamertemplate*{institute}\fi
     \ifx\insertdate\@empty\else\usebeamertemplate*{date}\fi
     \vfill
-    \vspace*{1mm}
+    \null
   \end{minipage}
 }
 %    \end{macrocode}