ExtUI Mesh Leveling Extensions (#13363)

Marlin/src/feature/bedlevel/mbl/mesh_bed_leveling.cpp

@@ -47,6 +47,11 @@
   void mesh_bed_leveling::reset() {
     z_offset = 0;
     ZERO(z_values);
+    #if ENABLED(EXTENSIBLE_UI)
+      for (uint8_t x = 0; x < GRID_MAX_POINTS_X; x++)
+        for (uint8_t y = 0; y < GRID_MAX_POINTS_Y; y++) 
+            ExtUI::onMeshUpdate(x, y, 0);
+    #endif
   }
 
   #if IS_CARTESIAN && DISABLED(SEGMENT_LEVELED_MOVES)