scanner: handle missing newline at EOF

scanner: handle missing newline at EOF

If there is no newline at EOF, we can see EOF immediately after
a valid symbol.  This can lead to calling close_token() when
state->node is NULL, which crashes.
The code in close_token() only makes sense if state->node is still the
same as token->node.  If it isn't, the token must be at the very end of
its code-node, so a different calculation is needed.

This avoids the NULL deref.

Signed-off-by: NeilBrown <neil@brown.name>