QuickMeasure: Do not measure datums

src/Mod/Measure/Gui/QuickMeasure.cpp

@@ -40,6 +40,7 @@
 
 #include <Mod/Part/App/PartFeature.h>
 #include <Mod/Part/App/TopoShape.h>
+#include <Mod/Part/App/DatumFeature.h>
 
 #include <Mod/Measure/App/Measurement.h>
 
@@ -133,8 +134,8 @@ bool QuickMeasure::shouldMeasure(const Gui::SelectionChanges& msg) const
 
 bool QuickMeasure::isObjAcceptable(App::DocumentObject* obj)
 {
-    // only measure shapes
-    if (obj && obj->isDerivedFrom(Part::Feature::getClassTypeId())) {
+    // only measure shapes. Exclude datums that derive from Part::Feature
+    if (obj && obj->isDerivedFrom<Part::Feature>() && !obj->isDerivedFrom<Part::Datum>()) {
         return true;
     }