message: Fix a null/undefined mismatch
diff: @@ -171,7 +171,7 @@ export default class SemanticTokensProvider extends AbstractProvider implements
  async provideDocumentSemanticTokens(document: vscode.TextDocument, token: vscode.CancellationToken): Promise<vscode.SemanticTokens | null> {
  - return this._provideSemanticTokens(document, null, token);
  + return this._provideSemanticTokens(document, undefined, token);
  }
  async provideDocumentRangeSemanticTokens(document: vscode.TextDocument, range: vscode.Range, token: vscode.CancellationToken): Promise<vscode.SemanticTokens | null> {
  @@ -189,7 +189,7 @@ export default class SemanticTokensProvider extends AbstractProvider implements
  return this._provideSemanticTokens(document, v2Range, token);
  }
  - async _provideSemanticTokens(document: vscode.TextDocument, range: protocol.V2.Range, token: vscode.CancellationToken): Promise<vscode.SemanticTokens | null> {
  + async _provideSemanticTokens(document: vscode.TextDocument, range: protocol.V2.Range | undefined, token: vscode.CancellationToken): Promise<vscode.SemanticTokens | null> {
  // We can only semantically highlight file from disk.
  if (document.uri.scheme !== "file") {
  return null;
  