Footprint Editor: make call to DXF importer not possible if a footprint does not exist, to avoid crash. ( It fixes an issue on Unity, where the file menu to call the DXF importer is not always disabled when no footprint loaded)

pcbnew/dialogs/dialog_export_vrml.cpp

@@ -242,7 +242,8 @@ void PCB_EDIT_FRAME::OnExportVRML( wxCommandEvent& event )
                           usePlainPCB, modelPath.GetPath(),
                           aXRef, aYRef ) )
     {
-        wxString msg = _( "Unable to create file " ) + fullFilename;
+        wxString msg;
+        msg.Printf( _( "Unable to create file '%s'" ), GetChars( fullFilename ) );
         wxMessageBox( msg );
         return;
     }

pcbnew/modedit.cpp

@@ -839,8 +839,11 @@ void FOOTPRINT_EDIT_FRAME::Process_Special_Functions( wxCommandEvent& event )
         break;
 
     case ID_GEN_IMPORT_DXF_FILE:
-        InvokeDXFDialogModuleImport( this, GetBoard()->m_Modules );
-        m_canvas->Refresh();
+        if( GetBoard()->m_Modules )
+        {
+            InvokeDXFDialogModuleImport( this, GetBoard()->m_Modules );
+            m_canvas->Refresh();
+        }
         break;
 
     default:

pcbnew/moduleframe.cpp

@@ -171,6 +171,7 @@ BEGIN_EVENT_TABLE( FOOTPRINT_EDIT_FRAME, PCB_BASE_FRAME )
     EVT_MENU( ID_MENU_CANVAS_CAIRO, PCB_BASE_FRAME::SwitchCanvas )
     EVT_MENU( ID_MENU_CANVAS_OPENGL, PCB_BASE_FRAME::SwitchCanvas )
 
+    // UI update events.
     EVT_UPDATE_UI( ID_MODEDIT_DELETE_PART, FOOTPRINT_EDIT_FRAME::OnUpdateLibSelected )
     EVT_UPDATE_UI( ID_MODEDIT_SELECT_CURRENT_LIB, FOOTPRINT_EDIT_FRAME::OnUpdateSelectCurrentLib )
     EVT_UPDATE_UI( ID_MODEDIT_EXPORT_PART, FOOTPRINT_EDIT_FRAME::OnUpdateModuleSelected )