Crash: when-command crashed with SIGSEGV in XextFindDisplay()

[almostearthling]

When appears to crash at times during idle time detection:

SegvAnalysis:
 Segfault happened at: 0x7fadd3b65bc0 <XextFindDisplay+80>: cmp    %rbx,0x8(%rax)
 PC (0x7fadd3b65bc0) ok
 source "%rbx" ok
 destination "0x8(%rax)" (0x00002a02) not located in a known VMA region (needed writable region)!
 Stack memory exhausted (SP below stack segment)
SegvReason: writing NULL VMA

Since it happened more than once it deserves deeper investigation. Full crash report attached for further analysis.

_usr_bin_when-command.1000.crash.gz