Fixed null subscriptions exception, added change log

Author: makharch

src/ResourceGraph/ResourceGraph/ChangeLog.md

@@ -18,6 +18,7 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
+* Fixed the output print issue for `Search-AzGraph`. Fixed the issue when Search-AzGraph fails  when no subscriptions are stored in the context.
 
 ## Version 0.10.0
 * Changed output of `Search-AzGraph` to PSResourceGraphResponse which wrapped previous output under Data property.

src/ResourceGraph/ResourceGraph/Cmdlets/SearchAzureRmGraph.cs

@@ -150,7 +150,7 @@ public override void ExecuteCmdlet()
             IList<string> subscriptions = null;
             if (managementGroups == null)
             {
-                subscriptions = this.GetSubscriptions().ToList();
+                subscriptions = this.GetSubscriptions()?.ToList();
                 if (subscriptions != null && subscriptions.Count > SubscriptionLimit)
                 {
                     subscriptions = subscriptions.Take(SubscriptionLimit).ToList();
@@ -262,7 +262,7 @@ private IEnumerable<string> GetSubscriptions()
             }
 
             var accountSubscriptions = this.DefaultContext.Account.GetSubscriptions();
-            if (accountSubscriptions.Length > 0)
+            if (accountSubscriptions?.Length > 0)
             {
                 return accountSubscriptions;
             }

src/ResourceGraph/ResourceGraph/help/Search-AzGraph.md

@@ -64,7 +64,8 @@ A complex query on resources featuring field selection, filtering and summarizin
 
 ### Example 3
 ```powershell
-PS C:\> Search-AzGraph -Query 'project id, name' -SkipToken 'skiptokenvaluefromthepreviousquery=='
+PS C:\> $response = (Search-AzGraph -Query 'project id, name' -First 1000)
+PS C:\> Search-AzGraph -Query 'project id, name' -SkipToken $response.SkipToken
 
 
 id         : /subscriptions/1ef51df4-f8a9-4b69-9919-1ef51df4eff6/resourceGroups/Service-INT-b/providers/Microsoft.Compute/virtualMachineScaleSets/nt2
@@ -74,7 +75,7 @@ id         : /subscriptions/1ef51df4-f8a9-4b69-9919-1ef51df4eff6/resourceGroups/
 name       : egtopic-2
 ```
 
-A query with the skip token passed from the previous query results
+A query with the skip token passed from the previous query results. Please note that keeping id in the results is mandatory to get back a skip token.
 
 ### Example 4
 ```powershell