Test removing typerState's null check

Author: noti0na1

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -790,7 +790,6 @@ class Namer { typer: Typer =>
       if (Config.showCompletions && ctx.typerState != creationContext.typerState) {
         def levels(c: Context): Int =
           if (c.typerState eq creationContext.typerState) 0
-          else if ((c.typerState: TyperState | Null) == null) -1
           else if (c.outer.typerState == c.typerState) levels(c.outer)
           else levels(c.outer) + 1
         println(s"!!!completing ${denot.symbol.showLocated} in buried typerState, gap = ${levels(ctx)}")