Prevent opening files with file format 23 in read-only mode

CHANGELOG.md

@@ -7,12 +7,14 @@
 ### Fixed
 * <How do the end-user experience this issue? what was the impact?> ([#????](https://github.com/realm/realm-core/issues/????), since v?.?.?)
 * List KVO information was being populated for non-list collections ([PR #7378](https://github.com/realm/realm-core/pull/7378), since v14.0.0)
+* Opening file with file format 23 in read-only mode will crash ([#7388](https://github.com/realm/realm-core/issues/7388), since v14.0.0)
 
 ### Breaking changes
 * None.
 
 ### Compatibility
 * Fileformat: Generates files with format v24. Reads and automatically upgrade from fileformat v10. If you want to upgrade from an earlier file format version you will have to use RealmCore v13.x.y or earlier.
+  You cannot open files with an file format older than v24 in read-only mode.
 
 -----------
 

src/realm/group.cpp

@@ -325,7 +325,7 @@ int Group::get_target_file_format_version_for_session(int current_file_format_ve
     // individual file format versions.
 
     if (requested_history_type == Replication::hist_None) {
-        if (current_file_format_version == 23) {
+        if (current_file_format_version == 24) {
             // We are able to open these file formats in RO mode
             return current_file_format_version;
         }
@@ -419,7 +419,6 @@ int Group::read_only_version_check(SlabAlloc& alloc, ref_type top_ref, const std
         case 0:
             file_format_ok = (top_ref == 0);
             break;
-        case 23:
         case g_current_file_format_version:
             file_format_ok = true;
             break;