FEM: do not allow to add multiple soler with gui

src/Mod/Fem/FemCommands.py

@@ -58,6 +58,8 @@ def IsActive(self):
                 active = FreeCADGui.ActiveDocument is not None and self.part_feature_selected()
             elif self.is_active == 'with_solver':
                 active = FemGui.getActiveAnalysis() is not None and self.active_analysis_in_active_doc() and self.solver_selected()
+            elif self.is_active == 'with_analysis_without_solver':
+                active = FemGui.getActiveAnalysis() is not None and self.active_analysis_in_active_doc() and not self.analysis_has_solver()
             return active
 
         def results_present(self):
@@ -84,3 +86,14 @@ def solver_selected(self):
                 return True
             else:
                 return False
+
+        def analysis_has_solver(self):
+            solver = False
+            analysis_members = FemGui.getActiveAnalysis().Member
+            for o in analysis_members:
+                if o.isDerivedFrom("Fem::FemSolverObjectPython"):
+                    solver = True
+            if solver is True:
+                return True
+            else:
+                return False

src/Mod/Fem/_CommandFemSolverCalculix.py

@@ -41,7 +41,7 @@ def __init__(self):
                           'MenuText': QtCore.QT_TRANSLATE_NOOP("Fem_SolverCalculix", "Create FEM Solver CalculiX ..."),
                           'Accel': "S, C",
                           'ToolTip': QtCore.QT_TRANSLATE_NOOP("Fem_SolverCalculix", "Creates FEM Solver CalculiX")}
-        self.is_active = 'with_analysis'
+        self.is_active = 'with_analysis_without_solver'
 
     def Activated(self):
         FreeCAD.ActiveDocument.openTransaction("Create SolverCalculix")