Keep stack frames that have no parameter list

[SimonCropp]

ScrubStackTrace trims each at frame at its closing paren, but not every frame has one. NativeAOT renders unresolved frames as:

at MyApp!<BaseAddress>+0x1a2b3c

Both IndexOf calls return -1, so span[..(indexOfRight + 1)] keeps zero characters and the frame becomes an empty line — or the literal ...) under removeParams. Captured on main:

System.Exception: Boom
                                 <- the frame
at MyApp.Program.Main(String[] args)
                                 <- and this one vanished entirely, trailing newline trimmed

Frames with no parameter list are now emitted as they are. That also leaves the + in the offset alone — routing them through WriteReplacePlus would have rewritten +0x1a2b3c to .0x1a2b3c, since that helper exists to turn the nested type separator into a dot.

NoParens and NoParens_RemoveParams cover both paths, each mixing unresolved frames with a normal one. Verify.Tests (1301) passes.