bug when subtitle is empty

source/beamerx.sty

@@ -411,14 +411,14 @@
         \put(3,3){%
           \makebox(0,0)[lb]{%
             \begin{minipage}{0.5\paperwidth}\noindent%
-              \sffamily\footnotesize\polyauteursave%
+              \sffamily\footnotesize\polyauteursave\hspace*{0pt}%
             \end{minipage}%
           }%
         }%
         \put(157,3){%
           \makebox(0,0)[rb]{%
             \begin{minipage}{0.5\paperwidth}\noindent\flushright%
-              \sffamily\footnotesize\polydatesave%
+              \sffamily\footnotesize\polydatesave\hspace*{0pt}%
             \end{minipage}%
           }%
         }%
@@ -426,7 +426,7 @@
           \makebox(0,0)[rb]{%
             \begin{minipage}{0.75\paperwidth}\noindent\flushright%
               \Large\setlength{\baselineskip}{0.7\baselineskip}%
-              \sffamily\bfseries\MakeUppercaseWithNewline{\polytitresave}%
+              \sffamily\bfseries\MakeUppercaseWithNewline{\polytitresave}\hspace*{0pt}%
             \end{minipage}%
           }%
         }%
@@ -434,7 +434,7 @@
           \makebox(0,0)[rt]{%
             \begin{minipage}{0.75\paperwidth}\noindent\flushright%
               \setlength{\baselineskip}{0.7\baselineskip}%
-              \sffamily\polysoustitresave%
+              \sffamily\polysoustitresave\hspace*{0pt}%
             \end{minipage}%
           }%
         }%