fix possible crash (?) due to DateTime format

Author: xupefei

QuickLook.Common/Helpers/SettingHelper.cs

@@ -64,9 +64,16 @@ public static void Set(string id, object value, Assembly calling = null)
         private static T GetSettingFromXml<T>(XmlDocument doc, string id, T failsafe)
         {
             var v = doc.SelectSingleNode($@"/Settings/{id}");
-            var result = v == null ? failsafe : (T) Convert.ChangeType(v.InnerText, typeof(T));
 
-            return result;
+            try
+            {
+                var result = v == null ? failsafe : (T) Convert.ChangeType(v.InnerText, typeof(T));
+                return result;
+            }
+            catch (Exception)
+            {
+                return failsafe;
+            }
         }
 
         private static void WriteSettingToXml(XmlDocument doc, string id, object value)
@@ -81,7 +88,7 @@ private static void WriteSettingToXml(XmlDocument doc, string id, object value)
             {
                 var node = doc.CreateNode(XmlNodeType.Element, id, doc.NamespaceURI);
                 node.InnerText = value.ToString();
-                doc.SelectSingleNode(@"/Settings").AppendChild(node);
+                doc.SelectSingleNode(@"/Settings")?.AppendChild(node);
             }
 
             doc.Save(new Uri(doc.BaseURI).LocalPath);
@@ -97,7 +104,22 @@ private static XmlDocument GetConfigFile(string file)
                 CreateNewConfig(file);
 
             var doc = new XmlDocument();
-            doc.Load(file);
+            try
+            {
+                doc.Load(file);
+            }
+            catch (XmlException)
+            {
+                CreateNewConfig(file);
+                doc.Load(file);
+            }
+
+            if (doc.SelectSingleNode(@"/Settings") == null)
+            {
+                CreateNewConfig(file);
+                doc.Load(file);
+            }
+
             FileCache.Add(file, doc);
             return doc;
         }
@@ -110,6 +132,8 @@ private static void CreateNewConfig(string file)
                 writer.WriteStartElement("Settings");
                 writer.WriteEndElement();
                 writer.WriteEndDocument();
+
+                writer.Flush();
             }
         }
     }

QuickLook/App.xaml.cs

@@ -88,11 +88,11 @@ private void Application_Startup(object sender, StartupEventArgs e)
 
         private void CheckUpdate()
         {
-            if (DateTime.Now - SettingHelper.Get<DateTime>("LastUpdate") < TimeSpan.FromDays(7))
+            if (DateTime.Now.Ticks - SettingHelper.Get<long>("LastUpdateTicks") < TimeSpan.FromDays(7).Ticks)
                 return;
 
             Task.Delay(120 * 1000).ContinueWith(_ => Updater.CheckForUpdates(true));
-            SettingHelper.Set("LastUpdate", DateTime.Now);
+            SettingHelper.Set("LastUpdateTicks", DateTime.Now.Ticks);
         }
 
         private void RemoteCallShowPreview(StartupEventArgs e)