Thanks for this report. Solving this issue would have been harder w/o this report since the key piece of
information [1] didn't display on my system when I tried reproducing the problem (the problem reproduced
fine).

You can find a fix here https://github.com/scottjad/conkeror/commit/fce63028e67e1fccc7f30aca735a51df826aabb5

I'll push it upstream soon, just want to test it a bit more first.

AFAIU this issue only effects non-release channels so far.

I'm trying to change the title a bit, since it effects 47 as well. Not sure how well changing the title
will work.

[1] JavaScript warning: file:///opt/conkeror/components/application.js, line 225: flags argument of 
String.prototype.{search,match,replace} is no longer supported