Problem with strtok()

I was under the impression strtok was supposed to return NULL when it hits the end of a string. It's not doing it when it should here. I'm testing with a multiline edit control with only 1 line of text (no \n). It continues into the loop a second time even though it shouldn't. Any ideas?

Code:

GetWindowText(hCode, txtCode, sizeof(txtCode));
ParseCodes(txtCode, strlen(txtCode)

int ParseCodes(char* code, int length)
{
    u32 address[CODE_MAX_LINES], value[CODE_MAX_LINES], codevalue;
    char type[CODE_MAX_LINES];
    int i = 0, c = 0;
    char *codeline, codepart[20];
    length = RemoveChar(code, length, ' ');
    codeline = strtok(code, "\n");
    CheatDB.System = SYSTEM_N64;
    while (codeline != NULL)
    {
        switch(CheatDB.System)
        {
            case SYSTEM_N64: case SYSTEM_PS1:
            {
                if (strlen(codeline) != 12) { return 0; }
                if (!isHex(codeline)) { return 0; }
                strncpy(codepart,codeline, 2); codepart[2] = '\0';
                String2Hex(codepart, &codevalue);
                c++;
            } break;
        }
        codeline = strtok(NULL, "\n");
    }
}

And what is the value of codeline the second time through? (Or the first time, or code to begin with?)

Doh. I figured out what I was doing wrong. I had that function filtering the spaces out. It ended the string with a \n instead of a \0. Why do I even bother.