drm: Check if the allocation has succeeded before dereferencing newmode

We allocate memory in drm_display_mode_from_vic_index() and use it
without checking the pointer is valid. Fix that.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_edid.c

@@ -2580,6 +2580,9 @@ drm_display_mode_from_vic_index(struct drm_connector *connector,
 		return NULL;
 
 	newmode = drm_mode_duplicate(dev, &edid_cea_modes[cea_mode]);
+	if (!newmode)
+		return NULL;
+
 	newmode->vrefresh = 0;
 
 	return newmode;