[Ganesh/Abhishek] - fixed bug in specified color

[GaneshSPatil]

What changes have you made? Changes made while printing json with user specified colors Previously user was able to specify any color(invalid color) because of which all the data was printing as undefined

Added a check before printing data that if the user specified color is invalid then use the default colors.

Why do we need this change? To print the data with valid options and color schemes

Files Modified:

modified:   lib/prettyjson.js
modified:   test/prettyjson_spec.js