Support non action keyword for plugins

Flow.Launcher.Core/Plugin/PluginConfig.cs

@@ -27,7 +27,7 @@
             var allPluginMetadata = new List<PluginMetadata>();
             var directories = pluginDirectories.SelectMany(Directory.EnumerateDirectories);
 
             // todo use linq when diable plugin is implmented since parallel.foreach + list is not thread saft
             foreach (var directory in directories)
             {
                 if (File.Exists(Path.Combine(directory, "NeedDelete.txt")))
@@ -83,7 +83,7 @@
                         // If metadata's version greater than each duplicate's version, CompareTo > 0
                         var count = group.Where(x => metadata.Version.CompareTo(x.Version) > 0).Count();
 
                         // Only add if the meatadata's version is the highest of all duplicates in the group
                         if (count == group.Count() - 1)
                         {
                             unique_list.Add(metadata);
@@ -119,7 +119,7 @@
                 // for plugins which doesn't has ActionKeywords key
                 metadata.ActionKeywords ??= new List<string> { metadata.ActionKeyword };
                 // for plugin still use old ActionKeyword
-                metadata.ActionKeyword = metadata.ActionKeywords?[0];
+                metadata.ActionKeyword = metadata.ActionKeywords?.FirstOrDefault() ?? string.Empty;
             }
             catch (Exception e)
             {
@@ -135,7 +135,7 @@
 
             if (!File.Exists(metadata.ExecuteFilePath))
             {
                 API.LogError(ClassName, $"Execute file path didn't exist <{metadata.ExecuteFilePath}> for conifg <{configPath}");
                 return null;
             }