Fix crash in search context generator

SearchBox/SearchBox.cs

@@ -3,6 +3,7 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Newtonsoft.Json;
 using UnidecodeSharpFork;
@@ -170,7 +171,8 @@ namespace LibSearchBox
 			foreach ((int, string) token in tokenizer.IterateTokens())
 			{
 				ConcurrentDictionary<int, List<int>> tokenQuery = index.Query(token.Item2);
-				if (!tokenQuery.ContainsKey(pageId)) continue; // Don't bother if this page doesn't contain this token
+				if (tokenQuery == null || !tokenQuery.ContainsKey(pageId))
+					continue; // Don't bother if this page doesn't contain this token
 				offsets.AddRange(tokenQuery[pageId].Select((int offset) => new SearchOffset(token.Item2, offset)));
 			}
 			offsets.Sort((SearchOffset x, SearchOffset y) => x.Offset - y.Offset);
@@ -228,10 +230,14 @@ namespace LibSearchBox
 					
 					if (settings.Html) {
 						result = WebUtility.HtmlEncode(result);
-						string resultSearchable = result.Unidecode().ToLower();
-						foreach ((int, string) nextToken in tokenizer.IterateTokens()) {
-							// TODO: Insert html tags here
-							throw new NotImplementedException("HTML tag insertion hasn't been implemented yet");
+						
+						foreach((int, string) nextToken in tokenizer.IterateTokens()) {
+							result = Regex.Replace(
+								result,
+								Regex.Escape(nextToken.Item2),
+								$"<strong class='query-term'>{nextToken.Item2}</strong>",
+								RegexOptions.IgnoreCase // Also ignores accents, apparently
+							);
 						} 
 					}
 					
@@ -241,9 +247,9 @@ namespace LibSearchBox
 			);
 
 			// Add the separator at the beginning and end if we aren't at the bounds of the source document
-			if (snippets.First().Item1 > 0)
+			if (snippets.Count > 0 && snippets.First().Item1 > 0)
 				snippetsText.Insert(0, "");
-			if (snippets.Last().Item2 < source.Length)
+			if (snippets.Count > 0 && snippets.Last().Item2 < source.Length)
 				snippetsText.Add("");
 
 			return string.Join(