Fix UI flickering

See #350

Wox.Plugin/Result.cs

@@ -42,12 +42,22 @@ namespace Wox.Plugin
         /// </summary>
         public string PluginDirectory { get; internal set; }
 
-        public new bool Equals(object obj)
+        public override bool Equals(object obj)
         {
-            if (obj == null || !(obj is Result)) return false;
+            Result r = obj as Result;
+            if (r != null)
+            {
+                return string.Equals(r.Title, Title) && string.Equals(r.SubTitle, SubTitle);
+            }
+            else
+            {
+                return false;
+            }
+        }
 
-            Result r = (Result)obj;
-            return r.Title == Title && r.SubTitle == SubTitle;
+        public override int GetHashCode()
+        {
+            return (Title?.GetHashCode() ?? 0) ^ (SubTitle?.GetHashCode() ?? 0);
         }
 
         public override string ToString()