[github] Check progress manager disposed state before callback

Otherwise when dialog is closed various "already disposed" errors pop up

Issue: EA-122314

platform/dvcs-impl/src/com/intellij/dvcs/ui/CloneDvcsDialog.java

@@ -323,6 +323,7 @@ public abstract class CloneDvcsDialog extends DialogWrapper {
 
       @Override
       public void onSuccess() {
+        if (mySpinnerProgressManager.getDisposed()) return;
         if (!myNewRepositories.isEmpty()) {
           // otherwise editor content will be reset
           myRepositoryUrlCombobox.setSelectedItem(myRepositoryUrlField.getText());