[Turtle/TriG] The empty prefix is fine

[kaefer3000]

Name of the lexer
Turtle/TriG

Code sample

@prefix : <http://example.org/#> .

:this a :Test .

This data with a colon, preceded by the empty string, is valid.
Renders OK on GitHub, but not with Rogue, see:
Link to a Code Sample.

Additional context
The official Turtle grammar
The line where I would try a fix if I knew Ruby

[pyrmont]

@kaefer3000 That's indeed the right line. I gather there's no other use for :?

[kaefer3000]

From the top of my head, no. It may appear in a Literal, though. The following is weird, but valid.

@prefix : <http://example.org/#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

: a :AdditionalTest ;
  rdfs:comment ":-)"^^: .