Throw if the db is closed

Author: kriszyp

package.json

@@ -1,7 +1,7 @@
 {
   "name": "lmdb",
   "author": "Kris Zyp",
-  "version": "3.2.5",
+  "version": "3.2.6",
   "description": "Simple, efficient, scalable, high-performance LMDB interface",
   "license": "MIT",
   "repository": {

read.js

@@ -416,13 +416,15 @@ export function addReadMethods(
 		},
 
 		attemptLock(id, version, callback) {
+			if (!env.address) throw new Error('Can not operate on a closed database');
 			keyBytes.dataView.setUint32(0, this.db.dbi);
 			keyBytes.dataView.setFloat64(4, version);
 			let keySize = this.writeKey(id, keyBytes, 12);
 			return attemptLock(env.address, keySize, callback);
 		},
 
 		unlock(id, version, onlyCheck) {
+			if (!env.address) throw new Error('Can not operate on a closed database');
 			keyBytes.dataView.setUint32(0, this.db.dbi);
 			keyBytes.dataView.setFloat64(4, version);
 			let keySize = this.writeKey(id, keyBytes, 12);