Free a memory block which has been allocated with av_malloc(z)() or
av_realloc() and set the pointer pointing to it to NULL.
@param ptr Pointer to the pointer to the memory block which should
be freed.
@note passing a pointer to a NULL pointer is safe and leads to no action.
@see av_free()
Free a memory block which has been allocated with av_malloc(z)() or av_realloc() and set the pointer pointing to it to NULL. @param ptr Pointer to the pointer to the memory block which should be freed. @note passing a pointer to a NULL pointer is safe and leads to no action. @see av_free()