randr: Do not update ConnectionInfo if NULL

RRScreenSizeNotify() will update the connection information block, but
if this occurs during initialization before ConnectionInfo is even
initialized, this will lead to a crash.

Simply check for ConnectionInfo prior to update it to avoid the crash.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95337
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>

randr/rrscreen.c

@@ -41,6 +41,9 @@ RREditConnectionInfo(ScreenPtr pScreen)
     int screen = 0;
     int d;
 
+    if (ConnectionInfo == NULL)
+        return;
+
     connSetup = (xConnSetup *) ConnectionInfo;
     vendor = (char *) connSetup + sizeof(xConnSetup);
     formats = (xPixmapFormat *) ((char *) vendor +