replace filter aborts rendering when the search string is empty #85

The replace filter calls Data.Text.replace, which raises error "Data.Text.replace: empty input" when the search string is empty. Jinja2's replace is total, so a template that passes an empty search argument renders in Jinja2 and aborts in ginger.

Reproduction

{{ ''|replace('','x') }}

Jinja2 renders x. ginger aborts:

runtime: Data.Text.replace: empty input
CallStack (from HasCallStack):
  error, called at libraries/text/src/Data/Text.hs:2108:18 in text-2.1.3-inplace:Data.Text

The same abort occurs when the search argument is missing or evaluates to the empty string.

Root cause

src/Text/Ginger/Run/Builtins.hs:327-342 (gfnReplace) calls the partial Data.Text.replace with search = asText searchG; a missing argument is defaulted to an empty value.