message: Allow GetType to return undefined
diff: @@ -28,7 +28,7 @@ export class StructureProvider extends AbstractSupport implements FoldingRangePr
  }
  }
  - GetType(type: string): FoldingRangeKind {
  + GetType(type: string): FoldingRangeKind | undefined {
  switch (type) {
  case "Comment":
  return FoldingRangeKind.Comment;
  @@ -37,7 +37,7 @@ export class StructureProvider extends AbstractSupport implements FoldingRangePr
  case "Region":
  return FoldingRangeKind.Region;
  default:
  - return null;
  + return undefined;
  }
  }
  