Don't create DiscardOrKeepProfileChangesDialog on start-up

Just whenever we need it, please.
This removes a warning from the start-up sequence, but the warning is still there when you open the dialogue. It's complaining that a model has size -13 and another has size -14, but I don't know which model that is. The UserChangesModel seems to be fine at a size of 1 or so.

Contributes to issue CURA-7501.

resources/qml/Cura.qml

@@ -838,17 +838,22 @@ UM.MainWindow
         }
     }
 
-    DiscardOrKeepProfileChangesDialog
+    Component
     {
-        id: discardOrKeepProfileChangesDialog
+        id: discardOrKeepProfileChangesDialogComponent
+        DiscardOrKeepProfileChangesDialog { }
+    }
+    Loader
+    {
+        id: discardOrKeepProfileChangesDialogLoader
     }
-
     Connections
     {
         target: CuraApplication
         onShowDiscardOrKeepProfileChanges:
         {
-            discardOrKeepProfileChangesDialog.show()
+            discardOrKeepProfileChangesDialogLoader.sourceComponent = discardOrKeepProfileChangesDialogComponent
+            discardOrKeepProfileChangesDialogLoader.item.show()
         }
     }
 

resources/qml/Dialogs/DiscardOrKeepProfileChangesDialog.qml

@@ -132,7 +132,7 @@ UM.Dialog
                 font.bold: true
             }
 
-            model: base.changesModel
+            model: userChangesModel
         }
     }