Fix #12195: Reset cursor when no Object is selected (#12207)

src/object_gui.cpp

@@ -441,6 +441,8 @@ public:
 
 		if (_selected_object_index != -1) {
 			SetObjectToPlaceWnd(SPR_CURSOR_TRANSMITTER, PAL_NONE, HT_RECT | HT_DIAGONAL, this);
+		} else {
+			ResetObjectToPlace();
 		}
 
 		this->UpdateButtons(_selected_object_class, _selected_object_index, _selected_object_view);