Possible bug with the tfun parser

[pesco]

The branch fix-many1-tfun contains a change to the transport function (ac1bcc3) that I made in the course of #7 in order to combine multiple transport_discard events into one. Unexpectedly this made the tfun parser fail, which it never should. I'm not sure if I'm overlooking something or whether this might point to a bug in the transport function or even the corresponding Hammer backend (LALR).

$ xxd -r -p samples/invalid.hex | build/dissect  
L> primary frame from master 0 to 1: UNCONFIRMED_USER_DATA: 40 C0 01 01 00 17 03
alloc context 1
tfun reset
T> (fir) segment 0: C0 01 01 00 17 03
tfun input: A
feed_tfun(...,0,1)
tfun init
tok index 0, ttok_pos=0
L> primary frame from master 0 to 1: UNCONFIRMED_USER_DATA: 82 41 43 42
T> (fin) segment 2: 41 43 42
tfun input: !Z
feed_tfun(...,0,2)
assertion "r != NULL" failed: file "/home/pesco/work/dnp3/src/dissect.c", line 273, function "feed_tfun"