migrated constants.dart to null safety

lib/core/constants.dart

@@ -1,5 +1,3 @@
-// @dart = 2.7
-
 const int thumbnailSmallSize = 256;
 const int thumbnailQuality = 50;
 const int thumbnailLargeSize = 512;

lib/services/search_service.dart

@@ -293,8 +293,11 @@ class SearchService {
       );
       if (matchedFiles.isNotEmpty) {
         searchResults.add(
-          GenericSearchResult(ResultType.event,
-              '$day ${potentialDate.item2.name} ${year ?? ''}', matchedFiles),
+          GenericSearchResult(
+            ResultType.event,
+            '$day ${potentialDate.item2.name} ${year ?? ''}',
+            matchedFiles,
+          ),
         );
       }
     }