Second attempt to fix a null pointer reference in deallocators of

built-in types (the first was in revision 21877).  When an exception
has raised within from the __init__ method of a user-defined class
derived from a built-in type (e.g., UnaryPredicate0D and
BinaryPredicate1D), some member variables of the base type are
left uninitialized, leading to a null pointer reference in the
"__dealloc__" function in the base type.  To avoid this, pointer
checking was added in the deallocators of those built-in types that
can be used to define a subclass by a user.

source/blender/freestyle/intern/python/UnaryFunction1D/BPy_UnaryFunction1DVec2f.cpp

@@ -163,7 +163,8 @@ int UnaryFunction1DVec2f___init__(BPy_UnaryFunction1DVec2f* self, PyObject *args
 }
 void UnaryFunction1DVec2f___dealloc__(BPy_UnaryFunction1DVec2f* self)
 {
-	delete self->uf1D_vec2f;
+	if (self->uf1D_vec2f)
+		delete self->uf1D_vec2f;
 	UnaryFunction1D_Type.tp_dealloc((PyObject*)self);
 }