Arguments of destroy_subtree() shall not be NULL
The arguments for rebalance_subtree() should not be NULL
The arguments for the rotation functions should not be NULL
The ptr arguments for remove_element() shouldnt be NULL
The attributes for the isolation functions should not be NULL either
The argument for the regen_metadata() function should not be NULL
The arguments for insert_elemeent_into_tree() shouldnt be NULL
The ptr attribute of find_node() should not be NULL