Fix NRE in Get-ScriptAnalyzerRule command (#691)

Author: Kapil Borle

Engine/Commands/GetScriptAnalyzerRuleCommand.cs

@@ -89,9 +89,16 @@ public string[] Severity
         /// </summary>
         protected override void BeginProcessing()
         {
+
+            // Initialize helper
+            Helper.Instance = new Helper(
+                SessionState.InvokeCommand,
+                this);
+            Helper.Instance.Initialize();
+
             string[] rulePaths = Helper.ProcessCustomRulePaths(customRulePath,
                 this.SessionState, recurseCustomRulePath);
-            ScriptAnalyzer.Instance.Initialize(this, rulePaths, null, null, null, null == rulePaths ? true : false);            
+            ScriptAnalyzer.Instance.Initialize(this, rulePaths, null, null, null, null == rulePaths ? true : false);
         }
 
         /// <summary>