Fix the Serialize button which was broken because field weren't properly initialized.

Author: bclothier

Rubberduck.Parsing/ComReflection/XmlComProjectSerializer.cs

@@ -17,20 +17,23 @@ public class XmlComProjectSerializer : IComProjectSerializationProvider
         public readonly string DefaultSerializationPath;
         private readonly IFileSystem _fileSystem;
 
-        public XmlComProjectSerializer(
-            IPersistencePathProvider pathProvider,
-            IFileSystem fileSystem)
+        private XmlComProjectSerializer(IFileSystem fileSystem, string defaultPath, string path)
         {
-            DefaultSerializationPath = pathProvider.DataFolderPath("Declarations");
             _fileSystem = fileSystem;
-        }
-
-        public XmlComProjectSerializer(IFileSystem filesystem, string path = null)
-        {
+            DefaultSerializationPath = defaultPath;
             Target = path ?? DefaultSerializationPath;
-            _fileSystem = filesystem;
         }
 
+        public XmlComProjectSerializer(
+            IPersistencePathProvider pathProvider,
+            IFileSystem fileSystem)
+            : this(fileSystem, pathProvider.DataFolderPath("Declarations"), null)
+        { }
+
+        public XmlComProjectSerializer(IFileSystem fileSystem, string path)
+            : this(fileSystem, path, path)
+        { }
+
         private static readonly XmlReaderSettings ReaderSettings = new XmlReaderSettings
         {
             CheckCharacters = false