Extratexts generate a line in the footprint even if the string is empty

[cnieves1]

This was raised by: KiCad/kicad-footprints#2143

In short, an extratexts line like:

L_Bourns_SRP5030T:
  description: "Inductor, Bourns, SRP5030T, 5.7mmx5.2mm"
  datasheet: "https://www.bourns.com/data/global/pdfs/SRP5030T.pdf"
  tags: "Inductor Bourns_SRP5030T"
  extratexts: [[-49.0, -0.05, "", "F.SilkS", 3.0, 3.0]]
  at: [-2.85, 2.60]
  size: [5.70, 5.20]
  smd_tht: "smd"
  pins: [["smd", "1", -2.25, 0, 2.0, 1.8, 0.0], ["smd", "2", 2.25, 0, 2.0, 1.8, 0.0]]

Generate a line in the footprint like:
(fp_text user "" (at -49 0.05) (layer F.SilkS)

Commenting out the extratexts line makes the generator fail:

KicadModTree/ModArgparser.py", line 134, in run self._parse_and_execute_yml(filepath)
    self._parse_and_execute_yml(filepath)
KicadModTree/ModArgparser.py", line 162, in _parse_and_execute_yml
   self._execute_script(**kwargs)  # now we can execute the script
KicadModTree/ModArgparser.py", line 255, in _execute_script
    parsed_args[k] = type(v.get('default'))

This adds nothing to the footprint, so can the script remove this line if the string is empty?