无法将类型Int的值赋给Swift 2.1中的Int数组元素

In my app I have ViewController class. In this class I have instance variable queue, which is array of type Int. In one of functions, I need to assign a value of type Int to the one of the elements of this array. The app builds without any errors and warnings, runs perfectly until it throws EXC_BREAKPOINT only in that place, where I have this assignment (in function called findPath). Here's the code:In my app I have ViewController class. In this