Hotfix tool mapping screen after refactoring FSM.

As a special exception we do not close PrintPreview screen when the LoadUnload dialog
is requested. It would destroy the ToolsMappingBody while one of its methods is still
executing, leading to calling refresh_physical_tool_filament_labels() which in turn
jumped to undefined memory.

src/gui/dialogs/DialogHandler.cpp

@@ -265,8 +265,16 @@ void DialogHandler::Loop() {
                 change(new_top->fsm_type, new_top->data);
             }
         } else {
-            close(old_top->fsm_type);
-            Screens::Access()->Loop();
+            if (new_top->fsm_type == ClientFSM::Load_unload && old_top->fsm_type == ClientFSM::PrintPreview) {
+                // TODO Remove this shitcode/prasohack as soon as possible.
+                //      As a special exception we do not close PrintPreview screen when the LoadUnload dialog
+                //      is requested. It would destroy the ToolsMappingBody while one of its methods is still
+                //      executing, leading to calling refresh_physical_tool_filament_labels() which in turn
+                //      jumped to undefined memory.
+            } else {
+                close(old_top->fsm_type);
+                Screens::Access()->Loop();
+            }
             open(new_top->fsm_type, new_top->data);
             Screens::Access()->Loop();
             change(new_top->fsm_type, new_top->data);