High: canseelogin() Unsafe String Comparison

[smooge]

Priority: HIGH
File: Src/checkX.c
Function: canseelogin()
Discovered: During unit testing of access control logic

Description: Function performs strcmp() without NULL checks on loginname global variable, potentially causing crashes if loginname is uninitialized.

Reproduction Steps:

1. Set loginname global variable to NULL
2. Set world.hide_login = 1
3. Call canseelogin()
4. Crashes due to strcmp(NULL, LOGIN)

Impact: Server crashes if loginname is not properly initialized, affecting system stability.

Proposed Fix: Add NULL safety checks:

int canseelogin(void) {
    if (loginname == NULL) {
        return 0;  /* Fail safe - deny access if user unknown */
    }
    return (!world.hide_login ||
            (strcmp(loginname, LOGIN) == 0) ||
            (strcmp(loginname, world.demigod) == 0));
}

Original Bug ID: BUG-002