Close to prevent hangs

ext/bg/js/database.js

@@ -96,6 +96,12 @@ class Database {
         }
     }
 
+    async close() {
+        this.validate();
+        this.db.close();
+        this.db = null;
+    }
+
     async purge() {
         this.validate();
 

test/test-database.js

@@ -130,6 +130,8 @@ async function testDatabase1() {
         // Cleanup
         await cleanup();
     }
+
+    await database.close();
 }
 
 async function testDatabaseEmpty1(database) {