Added an extra check to MLU bounds

Thanks to Ibrahim el-sayed for spotting the bug
void Type_Signature_Free(struct _cms_typehandler_struct* self, void* Ptr)
{
    _cmsFree(self ->ContextID, Ptr);
}

void Type_Signature_Free(struct _cms_typehandler_struct* self, void* Ptr)
{
    _cmsFree(self ->ContextID, Ptr);
}
