Universal implementation

[ByteBenderPro]

The following implementation is universal and does not case about string sizes. This should be used.

bool is_isogram(const char phrase[]){
    for(int i = 0; phrase[i] != '\0'; i++) {
        for(int c = 0; phrase[c] != '\0'; c++) {
            if ((toLowerCase(phrase[i]) == toLowerCase(phrase[c])) && (c != i) && isChar(phrase[i])) {
                return false;
            }
        }
    }
    return true;
}