There was definitely a bug with that line of code. So you changed the intention of the code a little. here's what it looks like with your new code below. I selected the top 2 waves (9814, 9815) and clicked "subtract wave front" which is the only place this code you edited is used.

As you can see it only gives me the option of subtracting out the remaining wavefront(s) which is just wavefront 9816.

The "old" broken code never subtracted out anything from the gui list. This bug goes back way before #193. For example, the bug exists in version 7.2.3

But the old code appears to try to only subtract out the first selected wave.

I like the way your new code works. I just want to double check with @githubdoe that he likes this new method where it removes all selected wavefronts from the gui list. Do you agree that this is good dale? Should the gui show:

1. all wavefronts
2. all wavefronts minus the selected wavefronts
3. all wavefronts minus the first selected wavefront

I think (2) is what we want and (2) is what Julien did.

I changed my mind on this. Not only do I like this fix, if someone really wants to subtract a wavefront from itself they can just load it twice and give it a different name. Or they can rotate it by 0 degrees (which is one way to make a copy of a wavefront). I'm going to go ahead and merge this fix.

For subtract function I wanted all wave fronts except the selected one but never got around to implementing that.