message: fix(language-service): guard access to `Symbol.members`
  Fixes
  What is the current behavior?
  The language service access TypeScript's Symbol.members without checking for null or undefined.
  What is the new behavior?
  The access is guarded.
diff: @@ -668,7 +668,7 @@ class TypeScriptSymbolQuery implements SymbolQuery {
  getSpanAt(line: number, column: number): Span { return spanAt(this.source, line, column); }
  private getTemplateRefContextType(type: ts.Symbol): ts.Symbol {
  - const constructor = type.members['__constructor'];
  + const constructor = type.members && type.members['__constructor'];
  if (constructor) {
  const constructorDeclaration = constructor.declarations[0] as ts.ConstructorTypeNode;
  for (const parameter of constructorDeclaration.parameters) {
  