pkg/55013: spectrwm crashes when attempting to start any X program

[fixerb@national.shitposting.agency]

>Number:         55013
>Category:       pkg
>Synopsis:       spectrwm crashes when attempting to start any X program
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 24 19:15:00 +0000 2020
>Originator:     fixerb
>Release:        NetBSD 9.0
>Organization:
>Environment:
NetBSD localhost 9.0 NetBSD 9.0 (EEEPC) #1: Sat Feb 22 12:28:38 CET 2020 fixerb@localhost:/usr/src/sys/arch/i386/compile/EEEPC i386
>Description:
Attempting to start any X11 program through spectrwm causes it to segfault (on i386 at least). The only exception I was able to find was dmenu, but for some reason starting programs through it crashes spectrwm too (dmenu itself seems okay, works perfectly otherwise).
GDB's backtrace shows that at the very end it crashes at strtonum() in libc and after finding out this I realized that during compilation there's actually a warning about an implicit declaration of such function.

spectrwm.c:6587:16: warning: implicit declaration of function 'strtonum'; did you mean 'strtouq'? [-Wimplicit-function-declaration]
ws_idx = (int)strtonum(q, 1, workspace_limit, &errstr);
>How-To-Repeat:
Build spectrwm from pkgsrc-2019Q4 and try to launch any X program from it.
>Fix: