Prevent possible null reference exception

* Prevent possible null referrence exception in `SelectItems.GetItems()`
* Other Minor changes

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelperService.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
@@ -130,7 +130,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form
 
             if (!selectItems.Any(si => si.Selected))
             {
-                var itemToBeSelected = selectItems.FirstOrDefault(si => si.Value.ToString() == selectedValue);
+                var itemToBeSelected = selectItems.FirstOrDefault(si => si.Value == selectedValue);
 
                 if (itemToBeSelected != null)
                 {

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/SelectItems.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Mvc.Rendering;
@@ -23,16 +23,16 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form
             while (properties.Count == 0)
             {
                 explorer = explorer.Container;
-                properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName.Equals(ItemsListPropertyName)).ToList();
-
                 if (explorer.Container == null)
                 {
                     return null;
                 }
+
+                properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName.Equals(ItemsListPropertyName)).ToList();
             }
 
             var selectItems = (properties.First().Model as IEnumerable<SelectListItem>).ToList();
-            
+
             return selectItems;
         }
     }

framework/src/Volo.Abp.AspNetCore/Volo/Abp/AspNetCore/ExceptionHandling/DefaultExceptionToErrorInfoConverter.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -42,9 +42,9 @@ namespace Volo.Abp.AspNetCore.Mvc.ExceptionHandling
         {
             var errorInfo = CreateErrorInfoWithoutCode(exception);
 
-            if (exception is IHasErrorCode)
+            if (exception is IHasErrorCode hasErrorCodeException)
             {
-                errorInfo.Code = (exception as IHasErrorCode).Code;
+                errorInfo.Code = hasErrorCodeException.Code;
             }
 
             return errorInfo;

framework/src/Volo.Abp.Core/Volo/Abp/Threading/AsyncHelper.cs

@@ -24,7 +24,7 @@ namespace Volo.Abp.Threading
 
         public static bool IsTaskOrTaskOfT([NotNull] this Type type)
         {
-            return type == typeof(Task) || type.GetTypeInfo().IsGenericType && type.GetGenericTypeDefinition() == typeof(Task<>);
+            return type == typeof(Task) || (type.GetTypeInfo().IsGenericType && type.GetGenericTypeDefinition() == typeof(Task<>));
         }
 
         /// <summary>