Fixed NullReferenceException

Author: madskristensen

src/toolkit/Community.VisualStudio.Toolkit.Shared/MEF/TokenErrorTaggerBase.cs

@@ -59,7 +59,7 @@ public override IEnumerable<ITagSpan<IErrorTag>> GetTags(NormalizedSnapshotSpanC
             }
         }
 
-        private static string GetErrorType(IList<ErrorListItem> errors)
+        private static string GetErrorType(IEnumerable<ErrorListItem> errors)
         {
             return errors.FirstOrDefault()?.ErrorCategory ?? PredefinedErrorTypeNames.SyntaxError;
         }

src/toolkit/Community.VisualStudio.Toolkit.Shared/MEF/TokenTag.cs

@@ -15,10 +15,10 @@ public class TokenTag : ITag
         /// <summary>
         /// Creates a new instance.
         /// </summary>
-        public TokenTag(object tokenType, params ErrorListItem[] errors)
+        public TokenTag(object tokenType, IEnumerable<ErrorListItem> errors)
         {
             TokenType = tokenType;
-            Errors = errors;
+            Errors = errors.ToList() ?? new();
         }
 
         /// <summary>
@@ -29,7 +29,7 @@ public TokenTag(object tokenType, params ErrorListItem[] errors)
         /// <summary>
         /// A list of errors associated with the tag.
         /// </summary>
-        public virtual IList<ErrorListItem> Errors { get; set; }
+        public virtual IEnumerable<ErrorListItem> Errors { get; set; }
 
         /// <summary>
         /// Returns true if there are no errors in the list.

src/toolkit/Community.VisualStudio.Toolkit.Shared/MEF/TokenTaggerBase.cs

@@ -70,7 +70,7 @@ public IEnumerable<ITagSpan<TokenTag>> GetTags(NormalizedSnapshotSpanCollection
         /// <param name="errors">Optional. List of errors associated with the token. This is used by the error tagger and will Error List.</param>
         public virtual TokenTag CreateToken(object tokenType, bool hasTooltip, bool supportOutlining, IEnumerable<ErrorListItem> errors)
         {
-            return new TokenTag(tokenType, errors.ToArray())
+            return new TokenTag(tokenType, errors)
             {
                 GetTooltipAsync = hasTooltip ? GetTooltipAsync : null,
                 GetOutliningText = supportOutlining ? GetOutliningText : null,
@@ -84,7 +84,7 @@ public virtual TokenTag CreateToken(object tokenType, bool hasTooltip, bool supp
         /// <returns><see langword="null"/>, or any text or WPF content to show in the tooltip (QuickInfo).</returns>
         public virtual Task<object> GetTooltipAsync(SnapshotPoint triggerPoint)
         {
-            return Task.FromResult<object>(null);
+            return Task.FromResult<object>(null!);
         }
 
         /// <summary>