Use "" for AppParameters if it's null

lib/ansible/modules/extras/windows/win_nssm.ps1

@@ -176,11 +176,13 @@ Function Nssm-Update-AppParameters
         Throw "Error updating AppParameters for service ""$name"""
     }
 
-    $appParametersHash = ParseAppParameters -appParameters $appParameters
-
     $appParamKeys = @()
     $appParamVals = @()
     $singleLineParams = ""
+    
+    if ($appParameters)
+    {
+        $appParametersHash = ParseAppParameters -appParameters $appParameters
         $appParametersHash.GetEnumerator() |
             % {
                 $key = $($_.Name)
@@ -196,15 +198,22 @@ Function Nssm-Update-AppParameters
                 }
             }
 
-    Set-Attr $result "nssm_app_parameters" $appParameters
         Set-Attr $result "nssm_app_parameters_parsed" $appParametersHash
         Set-Attr $result "nssm_app_parameters_keys" $appParamKeys
         Set-Attr $result "nssm_app_parameters_vals" $appParamVals
+    }
+
+    Set-Attr $result "nssm_app_parameters" $appParameters
     Set-Attr $result "nssm_single_line_app_parameters" $singleLineParams
 
     if ($results -ne $singleLineParams)
+    {
+        if ($appParameters)
         {
             $cmd = "nssm set ""$name"" AppParameters $singleLineParams"
+        } else {
+            $cmd = "nssm set ""$name"" AppParameters '""""'"
+        }
         $results = invoke-expression $cmd
 
         if ($LastExitCode -ne 0)