[applets kicker] Move safety check to a more useful place

The early return obviously needs to be before we use argument.at(0);

Found by the code quality checker on invent

applets/kicker/plugin/actionlist.cpp

@@ -345,6 +345,9 @@ bool handleRecentDocumentAction(KService::Ptr service, const QString &actionId,
     }
 
     const QStringList argument = _argument.toStringList();
+    if (argument.isEmpty()) {
+        return false;
+    }
     const auto resource = argument.at(0);
     const auto mimeType = argument.at(1);
 
@@ -362,10 +365,6 @@ bool handleRecentDocumentAction(KService::Ptr service, const QString &actionId,
         }
     }
 
-    if (argument.isEmpty()) {
-        return false;
-    }
-
     auto *job = new KIO::ApplicationLauncherJob(service);
     job->setUrls({QUrl::fromUserInput(resource)});
     job->setUiDelegate(new KNotificationJobUiDelegate(KJobUiDelegate::AutoHandlingEnabled));