outputconfigurationstore: fix choosing the default mode

The previous code kept the mode the backend had set as the default, but that's often not the
most ideal one


(cherry picked from commit 89278cdb12)

Co-authored-by: Xaver Hugl <xaver.hugl@gmail.com>

src/outputconfigurationstore.cpp

@@ -435,7 +435,7 @@ std::pair<OutputConfiguration, QList<Output *>> OutputConfigurationStore::genera
                 && mode->size() == existingData.mode->size
                 && mode->refreshRate() == existingData.mode->refreshRate;
         });
-        const auto mode = modeIt == modes.end() ? kscreenChangeSet.mode.value_or(output->currentMode()).lock() : *modeIt;
+        const auto mode = modeIt == modes.end() ? kscreenChangeSet.mode.value_or(chooseMode(output)).lock() : *modeIt;
 
         const auto changeset = ret.changeSet(output);
         *changeset = {