Added missing nullability annotations

Author: Sergio0694

Microsoft.Toolkit.Mvvm/ComponentModel/ObservableValidator.cs

@@ -67,7 +67,7 @@ protected ObservableValidator()
         /// be used to validate all properties, which will reference the current instance.
         /// </summary>
         /// <param name="items">A set of key/value pairs to make available to consumers.</param>
-        protected ObservableValidator(IDictionary<object, object> items)
+        protected ObservableValidator(IDictionary<object, object?> items)
         {
             this.validationContext = new ValidationContext(this, items);
         }
@@ -79,7 +79,7 @@ protected ObservableValidator(IDictionary<object, object> items)
         /// </summary>
         /// <param name="serviceProvider">An <see cref="IServiceProvider"/> instance to make available during validation.</param>
         /// <param name="items">A set of key/value pairs to make available to consumers.</param>
-        protected ObservableValidator(IServiceProvider serviceProvider, IDictionary<object, object> items)
+        protected ObservableValidator(IServiceProvider serviceProvider, IDictionary<object, object?> items)
         {
             this.validationContext = new ValidationContext(this, serviceProvider, items);
         }

Microsoft.Toolkit.Mvvm/Messaging/WeakReferenceMessenger.cs

@@ -408,7 +408,7 @@ public bool MoveNext()
                     {
                         // Get the key and value for the current node
                         if (node.Value.TryGetTarget(out TKey? target) &&
-                            this.owner.table.TryGetValue(target!, out TValue value))
+                            this.owner.table.TryGetValue(target!, out TValue? value))
                         {
                             this.node = node;
                             this.current = new KeyValuePair<TKey, TValue>(target, value);