Color Pattern String parsing fails when no `ledn` specified

[todbot]

Color pattern strings specified via the REST API like:

curl 'http://localhost:8934/blink1/pattern/add?pname=blink3green&pattern=3,%2300ff00,1.5,%23000000,0.5'

were being parsed incorrectly. The ledn parameter should be optional so the following should all be valid:

• 3,#00ff00,1.5,#000000,0.5 -- no ledn specified
• 3,#00ff00,1.5,1,#000000,0.5,0 -- ledn specifed for all color steps
• 3,#00ff00,1.5,1,#000000,0.5 -- ledn specified only sometimes

[todbot]

Should be fixed with 88a9dc57bd143371f147c964d787f1b6401a6a53