Fix a bug in Parser/Tree reference verification.
Fix a bug in Parser/Tree reference verification.

Signed-off-by: Jerome Dassonville <2f852d622deff8ec1a090ba3878db836c2b55ec6@gmail.com>

jdassonvil/sablecc,jdassonvil/sablecc,jdassonvil/sablecc,jdassonvil/sablecc,jdassonvil/sablecc