TechDraw: Use freecad_cast whenever possible

src/Mod/TechDraw/App/DrawViewDimension.cpp

@@ -729,7 +729,7 @@ double DrawViewDimension::getProjectedDimValue() const
 
     if (Type.isValue("Distance") || Type.isValue("DistanceX") || Type.isValue("DistanceY")) {
         pointPair pts = getLinearPoints();
-        auto dbv = dynamic_cast<DrawBrokenView*>(getViewPart());
+        auto dbv = freecad_cast<DrawBrokenView*>(getViewPart());
         if (dbv)  {
             // raw pts from view are inverted Y, so we need to un-invert them before mapping
             // raw pts are scaled, so we need to unscale them for mapPoint2dFromView