NullReferenceException related to sorting/paging

[ivanmonteiro]

Overview of the issue

I get the following NullReferenceException when viewing any listing page:

Exception has occurred: CLR/System.NullReferenceException
Ocorreu uma exceção do tipo "System.NullReferenceException" em JHipsterNet.dll, mas ela não foi manipulada no código do usuário: 'Object reference not set to an instance of an object.'
em JHipsterNet.Pagination.Binders.PageableBinder.ResolveSortArgument(QueryString queryString) em src\JHipsterNet\Pagination\Binders\PageableBinder.cs:linha 57
em JHipsterNet.Pagination.Binders.PageableBinder.ResolvePageableArgumentFromQueryString(QueryString queryString) em src\JHipsterNet\Pagination\Binders\PageableBinder.cs:linha 34
em JHipsterNet.Pagination.Binders.PageableBinder.BindModelAsync(ModelBindingContext bindingContext) em src\JHipsterNet\Pagination\Binders\PageableBinder.cs:linha 20
em Microsoft.AspNetCore.Mvc.ModelBinding.Binders.BinderTypeModelBinder.d__2.MoveNext()

Motivation for or Use Case

Reproduce the error

Using the latest master version, create some entities and go to the listing page of any of the created entities and the exception is thrown on the backend

Related issues

#176

Suggest a Fix

On QueryStringExtensions.cs file change GetParameterValues method:
To this:

        public static string[] GetParameterValues(this QueryString query, string name)
        {
            if (query == null || string.IsNullOrEmpty(name)) return new string[0];
            var parameters = QueryHelpers.ParseQuery(query.ToString());
            return parameters.ContainsKey(name) ? parameters[name].ToArray() :  new string[0];
        }

So the code that uses this method can safely run a foreach with the result without a null reference exeption.

JHipster Version(s)

JHipster configuration

Using master version of this repository

Entity configuration(s) entityName.json files generated in the .jhipster directory

Browsers and Operating System

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[nicolas63]

Can you create a PR with the fix and ask @maznag to review ?

[ivanmonteiro]

Can you create a PR with the fix and ask @maznag to review ?

I will do that this weekend