Add public IsAddressesSet method for WAFv2 UpdateIPSetRequest to handle empty list.

Author: ashishdhingra

generator/ServiceModels/wafv2/wafv2.customizations.json

@@ -0,0 +1,7 @@
+{
+  "emitIsSetProperties": {
+    "UpdateIPSetRequest": [
+      "Addresses"
+    ]
+  }
+}

sdk/src/Services/WAFV2/Generated/Model/UpdateIPSetRequest.cs

@@ -145,10 +145,32 @@ public List<string> Addresses
             set { this._addresses = value; }
         }
 
+        /// <summary>
+        /// This property is set to true if the property <seealso cref="Addresses"/>
+        /// is set; false otherwise.
+        /// This property can be used to determine if the related property
+        /// was returned by a service response or if the related property
+        /// should be sent to the service during a service call.
+        /// </summary>
+        /// <returns>
+        /// True if the related property was set or will be sent to a service; false otherwise.
+        /// </returns>
+        public bool IsAddressesSet
+        {
+            get
+            {
+                return Amazon.Util.Internal.InternalSDKUtils.GetIsSet(this._addresses);
+            }
+            set
+            {
+                Amazon.Util.Internal.InternalSDKUtils.SetIsSet(value, ref this._addresses);
+            }
+        }
+
         // Check to see if Addresses property is set
         internal bool IsSetAddresses()
         {
-            return this._addresses != null && this._addresses.Count > 0; 
+            return this.IsAddressesSet; 
         }
 
         /// <summary>