message: fix(language-service): do not crash when hovering over a label definitions
  Fixes:
diff: @@ -68,7 +68,7 @@ export function locateSymbol(info: TemplateInfo): SymbolInfo|undefined {
  }
  },
  visitReference(ast) {
  - symbol = info.template.query.getTypeSymbol(tokenReference(ast.value));
  + symbol = ast.value && info.template.query.getTypeSymbol(tokenReference(ast.value));
  span = spanOf(ast);
  },
  visitVariable(ast) {},
  