fix(parsing): handle edge case of blank strings as keys

[Cohedrin]

Fixes edge case of blank strings being keys. Not sure why this would ever happen, but heres some test data.

meta.txt

Edit:

Output of this specific case before:

> BinaryKVParser.parse(fs.readFileSync('meta.txt'))
Error: Unknown KV type 49 encountered at offset 25

Expected output

{ '':
   { 'members:numMachines': '1',
     'members:numPlayers': '1',
     'members:numSlots': '10',
     uids: '����\u0001',
     'system:netflag': 'teamlobby',
     'system:network': 'LIVE',
     'system:access': 'public',
     'game:type': 'classic',
     'game:mode': 'competitive',
     'game:mapgroupname': 'mg_de_dust2,mg_de_train,mg_de_nuke,mg_de_mirage,mg_de_cache,mg_de_overpass,mg_de_cbble',
     'game:map': 'de_dust2',
     'game:prime': '1',
     'game:nby': '1',
     'game:state': 'lobby',
     'game:search_key': 'k13565',
     'game:ark': '0',
     'game:apr': '0',
     'game:loc': 'US',
     'options:anytypemode': '0',
     'options:server': 'official' } }

uids is still not parsed properly, but seems to be consistent with other parsers (i.e. https://github.com/ValvePython/vdf and https://github.com/SteamRE/SteamKit/blob/master/SteamKit2/SteamKit2/Types/KeyValue.cs#L850

[DoctorMcKay]

Did you test this against typical input that previously parsed fine?

[Cohedrin]

I did yes, I tested it against some test cases I found in other libs, for example here and the other binarykv's I'm using.

Test script for old data (from the above link):

const BinaryKVParser = require('binarykvparser');
var str = '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';
var buf = new Buffer(str, 'base64')'
BinaryKVParser.parse(buf);

Should output:

{ '5':
   { billingtype: 3,
     changenumber: 1796623,
     codeclass: 1,
     gamecode: 3,
     licensetype: 1,
     packageid: 5,
     status: 0,
     territorycode: 0,
     extended: { DevComp: 1, OnPurchaseGrantGuestPassPackage1: 292 },
     appids: [ 10, 20, 30, 40, 50, 60, 70, 130, 211, 215, 218, 220, 240, 320, 340, 254430 ],
     depotids: [ 0, 221, 241, 263, 341, 254431 ],
     AppItems: [] } }

[DoctorMcKay]

Perfect. I'll go ahead and publish this then.