Fix nullable warnings

Author: Odotocodot

Flow.Launcher.Plugin.OneNote/Keywords.cs

@@ -26,6 +26,8 @@ public class Keyword
         public int Length => Value.Length;
         public static implicit operator string(Keyword keyword) => keyword.Value; 
         public override string ToString() => Value;
+
+        public static Keyword Empty { get; } = new ("");
     }
 
     //Needed for legacy as keywords where just saved as a string

Flow.Launcher.Plugin.OneNote/Search/DefaultSearch.cs

@@ -5,7 +5,7 @@
 namespace Flow.Launcher.Plugin.OneNote.Search
 {
 	public class DefaultSearch(PluginInitContext context, Settings settings, ResultCreator resultCreator)
-		: SearchBase(context, settings, resultCreator, null)
+		: SearchBase(context, settings, resultCreator, Keyword.Empty)
 	{
 		public override List<Result> GetResults(Query query)
 		{

Flow.Launcher.Plugin.OneNote/Search/SearchBase.cs

@@ -2,16 +2,13 @@
 
 namespace Flow.Launcher.Plugin.OneNote.Search
 {
-	public abstract class SearchBase(PluginInitContext context, Settings settings, ResultCreator resultCreator, Keyword? keyword)
+	public abstract class SearchBase(PluginInitContext context, Settings settings, ResultCreator resultCreator, Keyword keyword)
 	{
 		protected readonly PluginInitContext context = context;
 		protected readonly Settings settings = settings;
 		protected readonly ResultCreator resultCreator = resultCreator;
-#nullable disable
 		public readonly Keyword keyword = keyword;
-#nullable restore
 		protected Keywords Keywords => settings.Keywords;
 		public abstract List<Result> GetResults(Query query);
-
 	}
 }