[xiphos-source] [crosswire/xiphos] f8ecf8: fix #958 check for null result of render_this_text()

[karl kleinpaste]

  Branch: refs/heads/master
  Home:   https://github.com/crosswire/xiphos
  Commit: f8ecf86bd69835eff2265573d6d2e92f0171029f
      https://github.com/crosswire/xiphos/commit/f8ecf86bd69835eff2265573d6d2e92f0171029f
  Author: Karl Kleinpaste <karl at kleinpaste.org>
  Date:   2019-08-01 (Thu, 01 Aug 2019)

  Changed paths:
    M src/main/parallel_view.cc

  Log Message:
  -----------
  fix #958 check for null result of render_this_text()