[doc] change into includegraphicsmaybe in beji_battjes doc

examples/tomawac/beji_battjes/doc/beji_battjes.tex

@@ -85,7 +85,7 @@ without giving an substantial increase in calculation time.
 \label{bejiSpectra}
   \centering
     \includegraphics[width=0.9\textwidth]{bejiRes.png}
-		\includegraphics[width=0.9\textwidth]{../img/bejiSpec.png}
+    \includegraphicsmaybe{[width=0.9\textwidth]}{../img/bejiSpec.png}
       \caption{Wave spectra at 17 m (behind the bar) for the different
    simulations Top: measurement. Bottom: TOMAWAC result}
 \end{figure}