Preserve space after gHEAD

Author: jmbtutor

understanding-git.tex

@@ -277,7 +277,7 @@ \subsection{\gitcmd{commit}}
   \end{itemize}
   \vfill
   \begin{block}{\gHEAD{}}
-    A reference to the current branch or commit from which the working tree is derived. In other words, \gHEAD is what is currently checked out.
+    A reference to the current branch or commit from which the working tree is derived. In other words, \gHEAD{} is what is currently checked out.
   \end{block}
 \end{frame}