Calli with no arguments will crash dataflow analysis

[MichalStrehovsky]

We call PopUnknown with whatever is the number of parameters to the calli, but the first thing that PopUnknown does is that it will throw if this is less then 1.

https://github.com/mono/linker/blob/4f6f471f99189cb79f13a5b1ccfd3a26f81db601/src/linker/Linker.Dataflow/MethodBodyScanner.cs#L515-L516

I'm not sure we even use the return value of PopUnknown for anything, so maybe this can be simplified and doesn't have to throw (it's a thing taken from .NET Native analyzer verbatim if I remember correctly). I hit this while already yak shaving so I don't want to dig into this any further right now, just filing this for tracking.

Cc @vitek-karas

[MichalStrehovsky]

@LakshanF fixed this in #2091.