added test to create fts contentless table

test/fts-content.test.js

+/*jshint strict:true node:true es5:true onevar:true laxcomma:true laxbreak:true eqeqeq:true immed:true latedef:true*/
+(function () {
+  "use strict";
+
+  var sqlite = require('sqlite3')
+    , assert = require('assert')
+    , db
+    ;
+
+  function readyForQuery() {
+    db.exec('CREATE VIRTUAL TABLE t1 USING fts4(content="", a, b, c);', function (err) {
+      assert.ok(!err);
+    });
+  }
+
+  db = new sqlite.Database(":memory:", readyForQuery);
+}());