Fix some more UI crashes.

ICSharpCode.Decompiler/Metadata/MetadataResolver.cs

@@ -197,12 +197,16 @@ namespace ICSharpCode.Decompiler.Metadata
 					break;
 				case HandleKind.TypeReference:
 					var resolvedTypeReference = Resolve((TypeReferenceHandle)mr.Parent, context);
+					if (resolvedTypeReference.IsNil)
+						return default;
 					targetModule = resolvedTypeReference.Module;
 					targetMetadata = targetModule.Metadata;
 					declaringType = targetMetadata.GetTypeDefinition(resolvedTypeReference.Handle);
 					break;
 				case HandleKind.TypeSpecification:
 					resolvedTypeReference = Resolve((TypeSpecificationHandle)mr.Parent, context);
+					if (resolvedTypeReference.IsNil)
+						return default;
 					targetModule = resolvedTypeReference.Module;
 					targetMetadata = targetModule.Metadata;
 					declaringType = targetMetadata.GetTypeDefinition(resolvedTypeReference.Handle);
@@ -221,7 +225,7 @@ namespace ICSharpCode.Decompiler.Metadata
 						if (targetMetadata.StringComparer.Equals(fd.Name, name))
 							return new FieldDefinition(targetModule, f);
 					}
-					throw new NotSupportedException();
+					return default;
 				case MemberReferenceKind.Method:
 					var candidates = new List<(MethodDefinitionHandle, BlobHandle)>();
 					foreach (var m in declaringType.GetMethods()) {
@@ -229,15 +233,14 @@ namespace ICSharpCode.Decompiler.Metadata
 						if (targetMetadata.StringComparer.Equals(md.Name, name))
 							candidates.Add((m, md.Signature));
 					}
-					if (candidates.Count == 0)
-						throw new NotSupportedException();
 					foreach (var (method, signature) in candidates) {
 						if (SignatureBlobComparer.EqualsMethodSignature(targetMetadata.GetBlobReader(signature), metadata.GetBlobReader(mr.Signature), targetMetadata, metadata))
 							return new MethodDefinition(targetModule, method);
 					}
+					return default;
+				default:
 					throw new NotSupportedException();
 			}
-			throw new NotSupportedException();
 		}
 
 		public static TypeDefinition Resolve(this TypeSpecificationHandle handle, IMetadataResolveContext context)

ILSpy/MainWindow.xaml.cs

@@ -616,7 +616,7 @@ namespace ICSharpCode.ILSpy
 					}
 				case TypeReference tr:
 					var resolved = tr.Handle.Resolve(new SimpleMetadataResolveContext(tr.Module));
-					if (!resolved.IsNil)
+					if (resolved != null && !resolved.IsNil)
 						return assemblyListTreeNode.FindTypeNode(resolved);
 					return null;
 				case TypeSpecification ts:
@@ -626,7 +626,7 @@ namespace ICSharpCode.ILSpy
 					return null;
 				case MemberReference mr:
 					var resolvedMember = mr.Handle.Resolve(new SimpleMetadataResolveContext(mr.Module));
-					if (!resolvedMember.IsNil) {
+					if (resolvedMember != null && !resolvedMember.IsNil) {
 						switch (resolvedMember) {
 							case FieldDefinition fd:
 								return assemblyListTreeNode.FindFieldNode(fd);
@@ -639,7 +639,7 @@ namespace ICSharpCode.ILSpy
 					return null;
 				case MethodSpecification ms:
 					resolvedMember = ms.Handle.Resolve(new SimpleMetadataResolveContext(ms.Module));
-					if (!resolvedMember.IsNil) {
+					if (resolvedMember != null && !resolvedMember.IsNil) {
 						switch (resolvedMember) {
 							case MethodDefinition md:
 								return assemblyListTreeNode.FindMethodNode(md);

ILSpy/TreeNodes/BaseTypesEntryNode.cs

@@ -29,58 +29,48 @@ namespace ICSharpCode.ILSpy.TreeNodes
 		readonly Entity tr;
 		readonly GenericContext context;
 		readonly bool isInterface;
-		TypeDefinition td;
+		readonly bool showExpander;
+		readonly object icon;
 
 		public BaseTypesEntryNode(GenericContext context, Entity entity, bool isInterface)
 		{
 			if (entity.IsNil) throw new ArgumentNullException(nameof(entity));
 			this.tr = entity;
-			this.td = tr.ResolveAsType();
 			this.context = context;
 			this.isInterface = isInterface;
 			this.LazyLoading = true;
-		}
 
-		public override bool ShowExpander
-		{
-			get {
-				if (td.IsNil) return false;
+			var td = tr.ResolveAsType();
+			if (!td.IsNil) {
 				var typeDef = td.Module.Metadata.GetTypeDefinition(td.Handle);
-				return !typeDef.BaseType.IsNil || typeDef.GetInterfaceImplementations().Any();
+				showExpander = !typeDef.BaseType.IsNil || typeDef.GetInterfaceImplementations().Any();
+				icon = TypeTreeNode.GetIcon(td);
+			} else {
+				showExpander = false;
+				icon = isInterface ? Images.Interface : Images.Class;
 			}
 		}
 
+		public override bool ShowExpander => showExpander;
+
 		public override object Text
 		{
 			get { return this.Language.TypeToString(tr, context, includeNamespace: true) + tr.Handle.ToSuffixString(); }
 		}
 
-		public override object Icon
-		{
-			get
-			{
-				if (!td.IsNil)
-					return TypeTreeNode.GetIcon(td);
-				else
-					return isInterface ? Images.Interface : Images.Class;
-			}
-		}
+		public override object Icon => icon;
 
 		protected override void LoadChildren()
 		{
-			if (!td.IsNil)
+			var td = tr.ResolveAsType();
+			if (!td.IsNil) {
 				BaseTypesTreeNode.AddBaseTypes(this.Children, td);
+			}
 		}
 
 		public override void ActivateItem(System.Windows.RoutedEventArgs e)
 		{
-			// on item activation, try to resolve once again (maybe the user loaded the assembly in the meantime)
-			if (td.IsNil) {
-				td = tr.ResolveAsType();
-				if (!td.IsNil)
-					this.LazyLoading = true;
-				// re-load children
-			}
+			var td = tr.ResolveAsType();
 			e.Handled = ActivateItem(this, td);
 		}