The last two lines of the code snippet below represent a bug fix for a domdec corner case, where a domain may not have any angle terms. The bug can occur for systems with vacuum space (lipid monolayers, liquid:vapor), or systems with large numbers of molecules or particles w/o an angle term. The versions affected appear to be public beta versions c40b1 through c41b2, and alpha versions c41a1 through c42a2; the fix has been submitted, and should be in the August 2017 c42b2/c43a1 releases.
q_gromacs_style = .false.
q_charmm_style = .false.
! fix for domains with no angle terms
if (nangletbl==0) q_charmm_style = .true.