Undefined property: stdClass::$visibility_miles in _weather_parse_visibility() (line 601...

There is a special case when the visibility is very low, something under 1 mile, for example:
$metar_raw_string = 'KBLI 211420Z AUTO 00000KT 1/4SM R16/1800V3500FT FZFG VV001 M03/M04 A3022 RMK AO2';

In this case... we'll get a notice in logs because $metar->visibility_miles will not be initialized.

Everything that is past 1 mile, for example:

$metar_raw_string = 'KBLI 211420Z AUTO 00000KT 1 1/4SM R16/1800V3500FT FZFG VV001 M03/M04 A3022 RMK AO2'; will work.

I think that we can add a quick fix after line 599 in weather_parser.inc file:
instead of:

if ($matches[3] == '/') {
      // This is a fractional visibility, we need to convert this
      $visibility = $metar->visibility_miles + $matches[2] / $matches[4];
    }

we should check if $metar->visibility_miles is set or not, something like:

if ($matches[3] == '/') {
      if (!isset($metar->visibility_miles)) {
        $metar->visibility_miles = 0;
      }
      // This is a fractional visibility, we need to convert this
      $visibility = $metar->visibility_miles + $matches[2] / $matches[4];
    }