[TD]Handle missing XDirection on old files

src/Mod/TechDraw/App/DrawViewDetail.cpp

@@ -216,6 +216,15 @@ App::DocumentObjectExecReturn *DrawViewDetail::execute(void)
         return DrawView::execute();
     }
 
+    bool haveX = checkXDirection();
+    if (!haveX) {
+        //block touch/onChanged stuff
+        Base::Vector3d newX = getXDirection();
+        XDirection.setValue(newX);
+        XDirection.purgeTouched();  //don't trigger updates!
+        //unblock
+    }
+
     Base::Vector3d anchor = AnchorPoint.getValue();    //this is a 2D point (in unrotated coords)
     Base::Vector3d dirDetail = dvp->Direction.getValue();