Conditional Open Brace Produces Space

[Derek Thomas]

$ printf 'before open brace\n\.if 1 \\{\nwithin\n\\}\nafter\n.pl .p\n' | groff 
-Tascii
before open brace

within after
$

Why the blank line? Not a groff bug, admittedly---same behaviour with p9p 
nroff.  But any suggestions for a workaround? I've tried:

$ printf 'before open brace\n\.if 1 \\{\\\nwithin\n\\}\nafter\n.pl .p\n' | 
groff -Tascii
before open brace within after
$

---And this is fine in some cases.  But when the line following the open brace 
is a command or escape it sometimes causes problems.

$ groff --version
GNU groff version 1.19.2
...