Don't replace private values that haven't been set

(cherry picked from commit 52760e0908fa9852ed8a770f1916bb582eb8c8b4)
(cherry picked from commit 0c6eae256b76c9cb1462c6bc1acf6d49e9a28794)

src/Lidarr.Http/ClientSchema/SchemaBuilder.cs

@@ -27,15 +27,13 @@ namespace Lidarr.Http.ClientSchema
             foreach (var mapping in mappings)
             {
                 var field = mapping.Field.Clone();
+                field.Value = mapping.GetterFunc(model);
 
-                if (field.Privacy == PrivacyLevel.ApiKey || field.Privacy == PrivacyLevel.Password)
+                if (field.Value != null && !field.Value.Equals(string.Empty) &&
+                    (field.Privacy == PrivacyLevel.ApiKey || field.Privacy == PrivacyLevel.Password))
                 {
                     field.Value = PRIVATE_VALUE;
                 }
-                else
-                {
-                    field.Value = mapping.GetterFunc(model);
-                }
 
                 result.Add(field);
             }