add null check

Author: DeepakRajendranMsft

src/ResourceManager/Network/Commands.Network/NetworkInterface/NetworkInterfaceBaseCmdlet.cs

@@ -79,7 +79,7 @@ public PSNetworkInterface GetScaleSetNetworkInterface(string resourceGroupName,
 
 		public void NullifyApplicationSecurityGroupIfAbsent(NetworkInterface nic)
 		{
-			if (nic.IpConfigurations == null)
+			if (nic == null || nic.IpConfigurations == null)
 			{
 				return;
 			}

src/ResourceManager/Network/Commands.Network/NetworkSecurityGroup/NetworkSecurityGroupBaseCmdlet.cs

@@ -67,7 +67,7 @@ public PSNetworkSecurityGroup GetNetworkSecurityGroup(string resourceGroupName,
 		// Temporary - to be removed
 		public void NullifyApplicationSecurityGroupsIfAbsent(NetworkSecurityGroup nsg)
 		{
-			if (nsg.SecurityRules == null)
+			if (nsg ==null || nsg.SecurityRules == null)
 			{
 				return;
 			}