Stop leaking overlayWin in PanoramiXCompositeGetOverlayWindow error paths

Stop leaking overlayWin in PanoramiXCompositeGetOverlayWindow error paths

Found by parfait 1.1 code analyzer:

Error: Memory leak (CWE 401)
   Memory leak of pointer 'overlayWin' allocated with malloc(72)
        at line 806 of composite/compext.c in function 'PanoramiXCompositeGetOverlayWindow'.
          pointer allocated at line 794 with malloc(72).
          <unknown> leaks when rc != 0 at line 804.
        at line 816 of composite/compext.c in function 'PanoramiXCompositeGetOverlayWindow'.
          pointer allocated at line 794 with malloc(72).
          <unknown> leaks when pOc == NULL at line 815.
        at line 825 of composite/compext.c in function 'PanoramiXCompositeGetOverlayWindow'.
          pointer allocated at line 794 with malloc(72).
          <unknown> leaks when cs->pOverlayWin == NULL at line 822
              and compCreateOverlayWindow(pScreen) == 0 at line 823.
        at line 834 of composite/compext.c in function 'PanoramiXCompositeGetOverlayWindow'.
          pointer allocated at line 794 with malloc(72).
          <unknown> leaks when rc != 0 at line 832.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>