Guard resource deletion in OuptutConfiguration::sendApplied

Summary:
A client (kscreen-doctor especially) can disconnect whilst kwin still
has an instance.

Test Plan:
Had reproducible crash on kscreen-doctor.
Now don't.

Reviewers: #kwin

Subscribers: kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D18248

src/wayland/server/outputconfiguration_interface.cpp

@@ -287,6 +287,9 @@ void OutputConfigurationInterface::setApplied()
 
 void OutputConfigurationInterface::Private::sendApplied()
 {
+    if (!resource) {
+        return;
+    }
     org_kde_kwin_outputconfiguration_send_applied(resource);
 }
 
@@ -299,6 +302,9 @@ void OutputConfigurationInterface::setFailed()
 
 void OutputConfigurationInterface::Private::sendFailed()
 {
+    if (!resource) {
+        return;
+    }
     org_kde_kwin_outputconfiguration_send_failed(resource);
 }