Description: The system detected an invalid pointer address when it tried to use a pointer argument of a call.
说明：尝试使用调用的一个指针参数时-系统检测到无效指针地址。
2
Also note that the else statements are needed, since a call to Free will make the next check to the same component index an invalid check.
还要注意的是，else语句是必需的，因为调用Free会使下次对同一组件索引的检验变成无效检验。
3
If one is not seen, the dummy value of -999.99F is sent back to the method consumer, which interprets the dummy value as a call for an invalid stock symbol.