ProgressIndicator may create more stars than desired

[pixelzoom]

I ran into this when adding some 'dev' mode features to balancing-chemical-equations.

ProgressIndicator's constructor looks like:

24 function ProgressIndicator( numStars, scoreProperty, perfectScore, options )

It observes scoreProperty, and computes the number of 'filled' stars like this:

44 var proportion = score / perfectScore; 45 var numFilledStars = Math.floor( proportion * numStars );

The problem here is that there's no check to verify that the score is <= perfectScore. If it's not, then it will create more stars than numStars.

[pixelzoom]

I added this assertion:

40 assert && assert( score <= perfectScore );

Assigning to @jbphet to review.

[jbphet]

The assert looks reasonable to me. Tested a sim that uses the progress indicator with assertions turned on and saw no spurious asserts. Closing.