Interactive legend instant app - allow simple toggling

[wayfaringrob]

Currently, when using unclassed colors symbology, you get an error when trying to use the interactive legend template:

I am using feature layers, though. Since my Median HH Income layer uses unclassed colors, it doesn't let me toggle it on or off. However, my population & density layer, which uses transparency by attribute, does allow for toggling.

It would make a lot more sense if this legend could simply toggle all layers as the name and description implies, rather than limiting it to certain types of layers.