drm/panel: mantix: Don't dereference NULL mode

Don't dereference mode which was just NULL checked.
Signed-off-by: NGuido Günther <agx@sigxcpu.org>
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/659158549f3c6cc1c71ceed0943e760e861c1206.1602584953.git.agx@sigxcpu.org

drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c

@@ -204,7 +204,7 @@ static int mantix_get_modes(struct drm_panel *panel,
 	if (!mode) {
 		dev_err(ctx->dev, "Failed to add mode %ux%u@%u\n",
 			default_mode.hdisplay, default_mode.vdisplay,
-			drm_mode_vrefresh(mode));
+			drm_mode_vrefresh(&default_mode));
 		return -ENOMEM;
 	}