Indexing out-of-range in file module

In `file.c`, there's 
```c
// insert null term
if (vec__cap(vbuf) >= vec__len(vbuf) + 1)
    ((char *)__vec__at(vbuf, 0))[vec__len(vbuf)] = '\0';
else
    *((char *)__vec__at(vbuf, vec__len(vbuf))) = '\0';
```

Why the F is the else block accessing the 'vec__len(vbuf)'th element, when clearly it's outside of the capacity of the vector? This is pure __STUPIDITY__!

Change it ASAP.