[colm] segfault during iter on stdin [noob]

[peter.reijnders at verpeteren.nl]

Hello

I tried to pickup colm because I realy like its potential.
Due to the lack of examples and documentation I am fiddeling along and I 
am currently stuck with a simple task.

I try to parse a simple list with bullets and get a segfault.



A simple markdown file 'input.md':

```
* A list:
	* thing 1
	* thing 2:
		* thing 2a
	* thing 3

* Another list:
	* thang 1
	* thang 2:
		* thang 2a
	* thang 3
```

A simple script 'bullets.lm':

```colm
#!/usr/bin/env colm

lex
	#ignore 			/space+/
	literal 			`* `: `\n `\t
	token ws	 		/ ' ' /
	token bullet		/ '*' /
	token colon 		/ ':' /
	token newline 		/ '\n' /
	token tab 			/ 't' /
	token indent 		/ tab* /
	token identifier	/[a-zA-Z_]+/
end

def item
	[bullet ws+ identifier ws* newline]
|	[bullet ws+ itemlist]

def itemlist
	[identifier ws* colon ws* newline itemlist]

def itemlists
	[itemlist newline+ itemlists]
|	[itemlist]
|	[]

parse Input: itemlists[ stdin ]

for Id: itemlist in Input {
	print( Id.identifier )
}
```

It compiles without problems, but crashes in the for loop.

```bash
$colm bullets.lm
$gdb ./bullets
...
(gdb) run <input.md
Starting program: /redacted/bullets <input.md

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7bafdb3 in iter_find (prg=0x55555575c010, psp=0x7fffffffbdc8, 
iter=0x55555576c160, try_first=1)
     at iter.c:363
363		if ( try_first && ( iter->ref.kid->tree->id == iter->search_id || 
any_tree ) ) {
(gdb) bt
#0  0x00007ffff7bafdb3 in iter_find (prg=0x55555575c010, 
psp=0x7fffffffbdc8, iter=0x55555576c160,
     try_first=1) at iter.c:363
#1  0x00007ffff7bb0090 in tree_iter_advance (prg=0x55555575c010, 
psp=0x7fffffffbdc8, iter=0x55555576c160)
     at iter.c:401
#2  0x00007ffff7bbc0bb in colm_execute_code (prg=0x55555575c010, 
exec=0x7fffffffe080, sp=0x55555576c160,
     instr=0x555555758736 <parser_rootCode+54> "\270\r") at 
bytecode.c:1998
#3  0x00007ffff7bb1fbb in colm_execute (prg=0x55555575c010, 
exec=0x7fffffffe080,
     code=0x555555758700 <parser_rootCode> "\378\b\001") at 
bytecode.c:413
#4  0x00007ffff7bcee18 in colm_run_program2 (prg=0x55555575c010, argc=1, 
argv=0x7fffffffe218, argl=0x0)
     at program.c:218
#5  0x00007ffff7bcee5f in colm_run_program (prg=0x55555575c010, argc=1, 
argv=0x7fffffffe218) at program.c:227
#6  0x0000555555556d8c in main (argc=1, argv=0x7fffffffe218) at 
bullets.c:799
(gdb)
```

What am I doing wrong?
I am using a freshly cloned colm version '83e3cbcb25' and gcc version 
'(Debian 6.3.0-18) 6.3.0 20170516'.
.
I'd apreciate some tips.

Peter Reijnders