I'm still on my movie rental program. I don't know what is causing this error. This coding for my customer list and movie list are nearly identical in format.
I don't think the problem is coming from the code you pasted.
Only thing I can see in the above code that would cause a serious problem is the potential buffer overflow (how big are 'stock' and 'clientele'? Are you sure you have room to add another one to the array?)
That and you also never put 'item' in 'clientele' in your addCustomer function.