Two days ago, a patch was sent to Guix updating libx11 to a newer
version in order to fix CVE-2020-14344.  This causes a segmentation
fault in Emacs when trying to start an X window.  After invoking GDB, I
found the offending line to be:

  /* Determine XIC style */
  xic_style = best_xim_style (FRAME_X_XIM_STYLES (f));

For some reason, FRAME_X_XIM_STYLES (f) returns NULL here and
best_xim_style fails when ARRAYELTS is called on it.  I've attached a
patch, that checks for this case.

Regards, 
Leo