Fix error dialog focus issues after dismissal on Steam Link

app/gui/NavigableMessageDialog.qml

@@ -0,0 +1,21 @@
+import QtQuick 2.0
+import QtQuick.Dialogs 1.2
+
+MessageDialog {
+    property Item originalFocusItem
+
+    onVisibleChanged: {
+        if (!isWindow) {
+            if (visible) {
+                originalFocusItem = window.activeFocusItem
+            }
+            else {
+                // We must force focus back to the last item for platforms without
+                // support for more than one active window like Steam Link. If
+                // we don't, gamepad and keyboard navigation will break after a
+                // dialog appears.
+                originalFocusItem.forceActiveFocus()
+            }
+        }
+    }
+}