Part: [skip ci] fix memory leaks

+ add convenience function GeometryExtension::copyPyObject()
+ make sure to destroy the clone when leaving getGeometry()

src/Mod/Part/App/GeometryExtension.cpp

@@ -28,6 +28,7 @@
 #include <Base/Tools.h>
 
 #include "GeometryExtension.h"
+#include "GeometryExtensionPy.h"
 
 using namespace Part;
 
@@ -37,6 +38,13 @@ GeometryExtension::GeometryExtension()
 {
 }
 
+PyObject* GeometryExtension::copyPyObject() const
+{
+    Py::Tuple tuple;
+    Py::Object obj = Py::asObject(const_cast<GeometryExtension*>(this)->getPyObject());
+    return static_cast<GeometryExtensionPy *>(obj.ptr())->copy(tuple.ptr());
+}
+
 TYPESYSTEM_SOURCE_ABSTRACT(Part::GeometryPersistenceExtension,Part::GeometryExtension)
 
 void GeometryPersistenceExtension::restoreNameAttribute(Base::XMLReader &reader)