Fix color transition memory leak

[MunkeyBalls]

Fix for a memory leak which could occur when a light does a color transition to itself.

Example of a transition being stuck:

{
  "transitions": [
    {
      "id": 1520,
      "period": 4294967295,
      "last_sent": 0,
      "bulb": {
        "device_id": 1,
        "group_id": 1,
        "device_type": "rgb_cct"
      },
      "type": "color",
      "current_color": [
        255,
        167,
        91
      ],
      "end_color": [
        255,
        167,
        91
      ],
      "step_sizes": [
        0,
        0,
        0
      ]
    },
}

600 #523

[MunkeyBalls]

Still testing, but first impressions are good. No transitions stuck yet after a few hours of use. Free-heap seems stable as well.

[sidoh]

Sweet! Can we remove finished all together?

Think this would be updating the condition to just check if (isFinished()) and removing finished from the header and constructor.

[sidoh]

Looks great! just the styling comment and should be good to merge.

Thanks for looking into this!

[MunkeyBalls]

No worries, happy to help and this means I can finally run the latest version :)