fix script constructor array check

src/script.js

@@ -6,7 +6,7 @@ var network = require('./network');
 
 var Script = function(data) {
     this.buffer = data || [];
-    if(!Array.isArray(data)) {
+    if(!Array.isArray(this.buffer)) {
       throw new Error('expect Script to be initialized with Array, but got ' + data)
     }
     this.parse();

test/script.js

@@ -7,11 +7,12 @@ describe('Script', function() {
       assert.ok(new Script([]))
     })
 
-    it('throws an error when input is not an array', function() {
-      assert.throws(function(){
-        new Script({})
+    it('works when nothing is passed in', function() {
+      assert.ok(new Script())
     })
+
+    it('throws an error when input is not an array', function() {
+      assert.throws(function(){ new Script({}) })
     })
   })
-
 })