Brunel 2.6: No line chart shown when the color field only has one unique value.

[cjiang-ibm]

To replicate the problem, use this Brunel link: http://brunelvis.mybluemix.net/try.html

1. Paste this data to the Data Table tab:
   mpg,cylinders,engine,horsepower,weight,acceleration,year,origin,name
   18,8,307,130,3504,12,70,USA,chevrolet chevelle malibu
   15,8,350,165,3693,11.5,70,American,buick skylark 320
   18,8,318,150,3436,11,70,American,plymouth satellite
   16,8,304,150,3433,12,70,American,amc rebel sst
   17,8,302,140,3449,10.5,70,American,ford torino
   15,8,429,198,4341,10,70,American,ford galaxie 500
   14,8,454,220,4354,9,70,American,chevrolet impala
   14,8,440,215,4312,8.5,70,American,plymouth fury iii
   14,8,455,225,4425,10,70,USA,pontiac catalina

Syntax: line x(weight) y(mpg) color(origin:[red, black])
You will see this line chart as expected:

2. replace field "origin" value in the first row and the last row in above data with "American" so all the values in field "origin" are "American" and run the following syntax:
   line x(weight) y(mpg) color(origin:[black])

Here is what I'm getting: