Fix don't try to create ObjectBox directory if already exists

lib/data/objectbox/objectbox_cache.dart

@@ -18,7 +18,10 @@ class ObjectBoxCache {
 
     final path = p.join(docsDir.path, baseDir, subDir);
     try {
-      Directory(path).createSync(recursive: true);
+      final directory = Directory(path);
+      if (!directory.existsSync()) {
+        Directory(path).createSync(recursive: true);
+      }
     } catch (e) {
       _logger.severe('Error creating ObjectCachePathDirectory: $e');
     }