Simple question concerning arrays (C-like language)

My problem is probably too simple for words, but I can't figure out what I am doing wrong. I am currently programming in NXC (Not Exactly C) for a LEGO mindstorm robot, and my code is supposed to have the robot decide autonomously wether or not it is standing upright. This by means of comparing sensor values stored in an array. Sadly, it hasn't even come close to that point, with errors all over the place and now a runtime error ('file error' when running the program, probably caused by indexing values in nonexistant arrays - that's what googling told me).

My code:

 Spoiler

Code:

task main()
     {

     SetSensorLowspeed(IN_1);              //define sensor
     int distance = SensorUS(IN_1);        //SensorUS is the same sensor as SensorLowspeed
    
     int array_distance[];                // declaring array
     int i = 0;
     int arraymax = 10;
    
     ArrayInit(array_distance, 0, arraymax) //initialise output array, I suspect it to go wrong here.

     while ( i <= 9) {
          array_distance[i] = distance;
          i++;
          Wait(50);
          }

     int a = 0;
     int b = 0;
    
     while (b <= arraymax) {
           NumOut(a, LCD_LINE1, array_distance[b]);    //printing array on LCD screen, parameters NumOut(x,y,value).
           b++;
           a += 4;
           }
     }

Help me please. Help will be appreciated.