Ensure test providers deal with missing callback early

tests/lib/indexeddb.js

@@ -17,6 +17,8 @@ function IndexedDBTestProvider(name) {
   var that = this;
 
   function cleanup(callback) {
+    callback = callback || function(){};
+
     if(!that.provider || _done) {
       return callback();
     }
@@ -27,7 +29,6 @@ function IndexedDBTestProvider(name) {
       that.provider.db.close();
     }
 
-    callback = callback || function(){};
     var request = indexedDB.deleteDatabase(name);
     function finished() {
       that.provider = null;

tests/lib/memory.js

@@ -4,6 +4,8 @@ function MemoryTestProvider(name) {
   var that = this;
 
   function cleanup(callback) {
+    callback = callback || function(){};
+
     that.provider = null;
     callback();
   }

tests/lib/websql.js

@@ -12,9 +12,12 @@ function WebSQLTestProvider(name) {
   var that = this;
 
   function cleanup(callback) {
+    callback = callback || function(){};
+
     if(!that.provider || _done) {
       return callback();
     }
+
     // Provider is there, but db was never touched
     if(!that.provider.db) {
       return callback();