Harden IDE: Avoid NoDenotaton.owner in makePackageObjPrefixExplicit

Author: odersky

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -220,7 +220,8 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
    */
   def makePackageObjPrefixExplicit(tpe: NamedType): Type = {
     def tryInsert(pkgClass: SymDenotation): Type = pkgClass match {
-      case pkgCls: PackageClassDenotation if !(tpe.symbol.maybeOwner is Package) =>
+      case pkgCls: PackageClassDenotation
+      if !tpe.symbol.maybeOwner.is(Package) && pkgCls.packageObj.exists =>
         tpe.derivedSelect(pkgCls.packageObj.termRef)
       case _ =>
         tpe