Unsigned eeprom mesh addresses

Marlin/src/module/configuration_store.cpp

       }
     #endif
 
-    int16_t MarlinSettings::meshes_start_index() {
+    uint16_t MarlinSettings::meshes_start_index() {
       return (datasize() + EEPROM_OFFSET + 32) & 0xFFF8;  // Pad the end of configuration data so it can float up
                                                           // or down a little bit without disrupting the mesh data
     }

Marlin/src/module/configuration_store.h

 
       #if ENABLED(AUTO_BED_LEVELING_UBL) // Eventually make these available if any leveling system
                                          // That can store is enabled
-        static int16_t meshes_start_index();
-        FORCE_INLINE static int16_t meshes_end_index() { return meshes_end; }
+        static uint16_t meshes_start_index();
+        FORCE_INLINE static uint16_t meshes_end_index() { return meshes_end; }
         static uint16_t calc_num_meshes();
         static int mesh_slot_offset(const int8_t slot);
         static void store_mesh(const int8_t slot);
 
       #if ENABLED(AUTO_BED_LEVELING_UBL) // Eventually make these available if any leveling system
                                          // That can store is enabled
-        static constexpr int16_t meshes_end = E2END - 128; // 128 is a placeholder for the size of the MAT; the MAT will always
-                                                           // live at the very end of the eeprom
+        static constexpr uint16_t meshes_end = E2END - 128; // 128 is a placeholder for the size of the MAT; the MAT will always
+                                                            // live at the very end of the eeprom
 
       #endif