Error with Vim 7.4 only on current 1.6 tag release, not on 1.5 tag

**Running version:** 
VIM - Vi IMproved 7.4 (2013 Aug 10, compiled Jun 14 2019 10:42:49)
Included patches: 1-207, 209-629
Modified by <bugzilla@redhat.com>


**Note, seeing this error:**

Error detected while processing function<SNR>37_IndentGuidesEnable..indent_guides#enable..indent_guides#init_script_vars..indent_guides#capture_highlight:
line    1:
E117:  Unknown function:  execute