Fix [#31465] Segmentation Fault when Ctrl+Up/Down arrow to restore size of 3d Viewport.

Simply added a check for NULL pointer...

source/blender/editors/render/render_update.c

@@ -127,7 +127,7 @@ void ED_render_engine_area_exit(ScrArea *sa)
 	for (ar = sa->regionbase.first; ar; ar = ar->next) {
 		RegionView3D *rv3d;
 
-		if (ar->regiontype != RGN_TYPE_WINDOW)
+		if (ar->regiontype != RGN_TYPE_WINDOW || !(ar->regiondata))
 			continue;
 		
 		rv3d = ar->regiondata;