groff: A missing backslash after \{ can create an extra empty page

[Bjarni Ingi Gislason]

                           Groff Bug Report

GROFF VERSION: 1.22.2
'current-groff' from 12th October 2013

MACHINE: laptop i586

OS: Linux 3.2.46-1-rt67-1 (Debian)

COMPILER: gcc (Debian 4.7.2-5) 4.7.2

INPUT FILES:
.if \n(.g \{
.de X
..
.\}
.TH NAME 1 "24 October 2013" "Groff Version 1.22.2 and earlier"

COMMAND LINE:
groff  -ww -b -mandoc -Z <input file>

DESCRIPTION OF INCORRECT BEHAVIOUR:

  If a backslash is missing after an ".if ... \{" an extra empty page
is produced

  Output:

x T ps
x res 72000 1 1
x init
x F /home/bg/opt/share/groff/1.22.2/tmac/eqnrc
x F -
x F ./prof.gro
p1
V817889
H72000
DFd
x font 5 TR
f5
s10000
h446275
md
t1
n12000 0
V841889
p1
x font 5 TR
f5
s10000
V48000
H72000
tN
H78870
tAME(1)
h128508
tGeneral
wh2500
tCommands
wh2500
tManual
h128507
tN
H489395
tAME(1)
n12000 0
V817889
H72000
tGrof
H90630
tf
wh2500
tV
H102570
tersion
wh2500
t1.22.2
wh2500
tand
wh2500
tearlier
h64543
t24
wh2500
tOctober
wh2500
t2013
h187032
t1
n12000 0
x trailer
V841889
x stop