QmlDesigner: Register stream operators for easing curves

EasingCurve::registerStreamOperators() was never called.

Change-Id: I2b84ea44c3faa350f36570d38fbdc64d4c5ce08d
Reviewed-by: Knud Dollereder <knud.dollereder@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmldesigner/qmldesignerextension/timelineeditor/timelineview.cpp

@@ -24,6 +24,8 @@
 ****************************************************************************/
 
 #include "timelineview.h"
+
+#include "easingcurve.h"
 #include "timelinecontext.h"
 #include "timelinewidget.h"
 
@@ -57,7 +59,9 @@ namespace QmlDesigner {
 
 TimelineView::TimelineView(QObject *parent)
     : AbstractView(parent)
-{}
+{
+    EasingCurve::registerStreamOperators();
+}
 
 TimelineView::~TimelineView() = default;