fix gc timeout

src/Database.js

@@ -79,7 +79,7 @@ export default function extendDatabase (Y /* :any */) {
 
       function garbageCollect () {
         return os.whenTransactionsFinished().then(function () {
-          if (os.gc1.length > 0 || os.gc2.length > 0) {
+          if (os.gcTimeout > 0 && (os.gc1.length > 0 || os.gc2.length > 0)) {
             if (!os.y.connector.isSynced) {
               console.warn('gc should be empty when not synced!')
             }
@@ -265,7 +265,7 @@ export default function extendDatabase (Y /* :any */) {
       }
     }
     * destroy () {
-      clearInterval(this.gcInterval)
+      clearTimeout(this.gcInterval)
       this.gcInterval = null
       this.stopRepairCheck()
     }

src/y.js

@@ -225,13 +225,13 @@ class YConfig {
     } else {
       this.connector.disconnect()
     }
-    return this.db.whenTransactionsFinished(function () {
-      this.db.destroyTypes()
+    return this.db.whenTransactionsFinished().then(function () {
+      self.db.destroyTypes()
       // make sure to wait for all transactions before destroying the db
-      this.db.requestTransaction(function * () {
+      self.db.requestTransaction(function * () {
         yield * self.db.destroy()
       })
-      return this.db.whenTransactionsFinished()
+      return self.db.whenTransactionsFinished()
     })
   }
 }