Unexpected exception in ALC interface

[raquelalvarezbanos]

This issue was originally TRAC 11780

In the peak fitting step, if you fit two peaks, then remove one of them from the function browser and hit the fit button again, an unexpected exception is thrown:

"Unknown function parameter"

This also happens in the BaselineModelling step.

[raquelalvarezbanos]

Looking deeper into this I've realized that there is a bug in FunctionBrowser rather than in ALC. I've checked that it also affects the MDF interface, as it uses a FunctionBrowser too. The problem is that when the user adds more than one function to the browser, a CompositeFunction is created (and an index fi is assigned to each function), but this CompositeFunction is not destroyed when only one function remains, so the remaining function keeps the f0 index, which causes the "Unknown function parameter" error, as the function parameters should still be referred to as f0.parameters.

I think the best way to solve this is to add an if statement in FunctionBrowser::removeFunction() to check the number of functions remaining in the browser.