feat: optimize and stabilize string normalization in StringMatcher

Enhance search reliability and performance by refining the Normalize method. - Added null/empty string handling to prevent NullReferenceExceptions during search.

Author: 4yinn

Flow.Launcher.Infrastructure/StringMatcher.cs

@@ -1,11 +1,12 @@
-using CommunityToolkit.Mvvm.DependencyInjection;
-using Flow.Launcher.Plugin.SharedModels;
-using System;
+using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using System.Text;
+using CommunityToolkit.Mvvm.DependencyInjection;
 using Flow.Launcher.Infrastructure.UserSettings;
+using Flow.Launcher.Plugin.SharedModels;
 
 namespace Flow.Launcher.Infrastructure
 {
@@ -256,14 +257,23 @@ public MatchResult FuzzyMatch(string query, string stringToCompare, MatchOption
         };
         public static string Normalize(string value)
         {
-            Span<char> buffer = stackalloc char[value.Length];
-            for (int i = 0; i < value.Length; i++)
+            if (string.IsNullOrEmpty(value)) return value;
+            char[] arrayFromPool = null;
+            Span<char> buffer = value.Length <= 512 ? stackalloc char[value.Length] : (arrayFromPool = ArrayPool<char>.Shared.Rent(value.Length));
+            try
             {
-                var c = char.ToLowerInvariant(value[i]);
-                buffer[i] = AccentMap.TryGetValue(c, out var mapped) ? mapped : c;
+                for (int i = 0; i < value.Length; i++)
+                {
+                    var c = char.ToLowerInvariant(value[i]);
+                    buffer[i] = AccentMap.TryGetValue(c, out var mapped) ? mapped : c;
+                }
+                return new string(buffer.Slice(0, value.Length));
+            }
+            finally
+            {
+                if (arrayFromPool != null)
+                    ArrayPool<char>.Shared.Return(arrayFromPool);
             }
-
-            return new string(buffer);
         }
         private static bool IsAcronym(string stringToCompare, int compareStringIndex)
         {