private static @Nullable PsiExpression getSingleEmptyStringArgument(PsiCall call) {
      PsiExpressionList argList = call.getArgumentList();
      if (argList == null) return null;
      PsiExpression[] args = argList.getExpressions();
      if (args.length != 1) return null;
      return ExpressionUtils.isLiteral(PsiUtil.skipParenthesizedExprDown(args[0]), "") ? args[0] : null;
    }
private static @Nullable PsiExpression getSingleEmptyStringArgument(PsiCall call)