Don't try to export when we don't have filters and fix mem leak when we cancel

src/filter/kmfilterdialog.cpp

@@ -784,19 +784,26 @@ void KMFilterDialog::slotExportAsSieveScript()
     KMessageBox::information(this, i18n("We cannot convert all KMail filters to sieve scripts but we can try :)"), i18n("Convert KMail filters to sieve scripts"));
     bool wasCanceled = false;
     const QList<MailFilter *> filters = mFilterList->filtersForSaving(false, wasCanceled);
-    QPointer<FilterSelectionDialog> dlg = new FilterSelectionDialog(this);
-    dlg->setFilters(filters);
-    if (dlg->exec() == QDialog::Accepted) {
-        QList<MailFilter *> lst = dlg->selectedFilters();
-        if (!lst.isEmpty()) {
-            FilterConvertToSieve convert(lst);
-            convert.convert();
-            qDeleteAll(lst);
-        } else {
-            KMessageBox::information(this, i18n("No filters selected."), i18n("Convert KMail filters to sieve scripts"));
+    if (!filters.isEmpty()) {
+        return;
+    }
+    if (!wasCanceled) {
+        QPointer<FilterSelectionDialog> dlg = new FilterSelectionDialog(this);
+        dlg->setFilters(filters);
+        if (dlg->exec() == QDialog::Accepted) {
+            QList<MailFilter *> lst = dlg->selectedFilters();
+            if (!lst.isEmpty()) {
+                FilterConvertToSieve convert(lst);
+                convert.convert();
+                qDeleteAll(lst);
+            } else {
+                KMessageBox::information(this, i18n("No filters selected."), i18n("Convert KMail filters to sieve scripts"));
+            }
         }
+        delete dlg;
+    } else {
+        qDeleteAll(filters);
     }
-    delete dlg;
 }
 
 void KMFilterDialog::slotHelp()