glxproxy: warning fix

glxcmds.c: In function ‘CreateGLXPixmap’:
glxcmds.c:1641:22: warning: ‘pGlxScreen’ may be used uninitialized in this function

Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>

hw/dmx/glxProxy/glxcmds.c

@@ -1733,6 +1733,7 @@ static int CreateGLXPixmap(__GLXclientState *cl,
     else {
        pVisual = NULL;
        pGlxVisual = NULL;
+       pGlxScreen = &__glXActiveScreens[pDraw->pScreen->myNum];
     }
 
     pGlxPixmap = (__GLXpixmap *) malloc(sizeof(__GLXpixmap));