accessing array's row 0

I have a matrix for the keyboard layout in my program as follows:

code unsigned char buttons[BUTTON_COUNT][KEY_TABLE_WIDTH]
            = {
                 {'8',        'u',        'ü',        'v',        EMPTY_CODE},
                 {'7',        'r',        's',        'ş',        't'},
                 {'6',        'ö',        'p',        'q',        EMPTY_CODE},
                 {'5',        'l',        'm',        'n',        'o'},
                 {'1',        'a',        'b',        'c',        'ç'},
                 {'2',        'd',        'e',        'f',        EMPTY_CODE},
                 {'3',        'g',        'ğ',        'h',        'ı'},
                 {'4',        'i',        'j',        'k',        EMPTY_CODE},
                 {'9',        'w',        'x',        'y',        'z'},
                 {'0',        ' ',        ':',        '-',        EMPTY_CODE},
                 {RIGHT_ARROW,EMPTY_CODE, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE},
                 {LEFT_ARROW, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE},
                 {ESC,        EMPTY_CODE, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE},
                 {DEL,        EMPTY_CODE, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE},
                 {CAPS,       EMPTY_CODE, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE},
                 {ENTER,      EMPTY_CODE, EMPTY_CODE, EMPTY_CODE, EMPTY_CODE}
              };

I use this table to use keyboard as in gsm phones to produce letters using 10 buttons.

Code works fine, but when I push on the button 0, it fails to access the row 0 of the array. I can get key '7', but cannot get key '8'. It finds 0x00 for the first row members.

I studied the code produced and tried to investigate using debugger; but they all seem OK to me. However, when I program the AT89C55WD with this code, it cannot find the keys (8, ...) for button 0. Please note all the other keys are OK.

I could not solve this problem, and inserted a dummy row to the table at row 0, and indexed the table with not the button pressed, but with (button+1).

This worked, but since it is just a work-around; I really wonder the reason.

Any ideas?