MainWindow: Use 'default-mage' (if exists) in case of last solver is not found.

src/View/MainWindow.py

@@ -363,12 +363,20 @@ class ApplicationWindow(QMainWindow, ListedSubWindow, WindowToolKit):
         self._last_solver = None
         self._last_results = None
 
+        default = None
+
         for solver in self.conf.solvers:
+            if solver.name == "default-mage":
+                default = solver
+
             if solver.name == self.conf.last_solver_name:
                 self._last_solver = solver
                 self.enable_actions("action_menu_results_last", True)
                 return
 
+        # Last solver note found, use default-mage if exists
+        self._last_solver = default
+
     def set_results(self, solver, results):
         self._last_solver = solver
         self._last_results = results