Black color bug in Heatmap

[lumizilla]

Hello, I am having a bug regarding colors on a heatmap. More details below.

Kibana version: 5.4.0

Elasticsearch version: 5.4.0

Server OS version: elementary OS 0.4 Loki (64 bit)

Browser version: Mozilla Firefox 50.1.0

Browser OS version: same as server

Original install method (e.g. download page, yum, from source, etc.): Download page.

Description of the problem including expected versus actual behavior: When checking 'scale to data bounds' field, the heatmap graph becomes entirely black (I expected it to be one of the heatmap colors). If I uncheck this option, the color becomes one of the colors specified on the heatmap (which was expected).

Steps to reproduce:

1. Insert the data present on elasticsearch's twitter example that is on github:

`curl -XPUT 'http://localhost:9200/twitter/user/kimchy?pretty' -H 'Content-Type: application/json' -d '{ "name" : "Shay Banon" }'

curl -XPUT 'http://localhost:9200/twitter/tweet/1?pretty' -H 'Content-Type: application/json' -d '
{
"user": "kimchy",
"post_date": "2009-11-15T13:12:00",
"message": "Trying out Elasticsearch, so far so good?"
}'

curl -XPUT 'http://localhost:9200/twitter/tweet/2?pretty' -H 'Content-Type: application/json' -d '
{
"user": "kimchy",
"post_date": "2009-11-15T14:12:12",
"message": "Another tweet, will it be indexed?"
}'`

2. On kibana, create an index for this example, and then go to: visualize -> create new visualization -> heatmap -> "twitter"

3. Change the time range to search for november/2009. Select the bucket "x-axis", with the aggregation "date histogram" with the interval "monthly". Under options, check "scale to data bounds". When running the new configurations, the graph should become black.

Here is a screenshot of the black graph with the "scale to data bounds" option (it should not be black):

And here is the graph when I uncheck the "scale the data bounds" option:

Thank you for your support.