small fixes

source/polytechnique.dtx

     \titleformat{\section}
         [display]
         {\color{rouge485}\LARGE\bfseries\sffamily\filcenter}
-        {\thesection}{0em}
+        {\thesection}
+        {0em}
         {\MakeUppercase}
         [\vspace*{-0.5\baselineskip}%
             \includegraphics{\polyfiletlongrouge}]
     \titleformat{\subsection}
-        [hang]
+        [block]
         {\color{bleu315}\Large\scshape}
         {\thesubsection}
         {0.5em}

source/polytechnique.sty

     \titleformat{\section}
         [display]
         {\color{rouge485}\LARGE\bfseries\sffamily\filcenter}
-        {\thesection}{0em}
+        {\thesection}
+        {0em}
         {\MakeUppercase}
         [\vspace*{-0.5\baselineskip}%
             \includegraphics{\polyfiletlongrouge}]
     \titleformat{\subsection}
-        [hang]
+        [block]
         {\color{bleu315}\Large\scshape}
         {\thesubsection}
         {0.5em}