Protect against end after destroy (#34)

Author: orgads

index.js

@@ -231,7 +231,7 @@ Duplexify.prototype.end = function(data, enc, cb) {
   if (typeof enc === 'function') return this.end(data, null, enc)
   this._ended = true
   if (data) this.write(data)
-  if (!this._writableState.ending) this.write(SIGNAL_FLUSH)
+  if (!this._writableState.ending && !this._writableState.destroyed) this.write(SIGNAL_FLUSH)
   return stream.Writable.prototype.end.call(this, cb)
 }
 

test.js

@@ -137,6 +137,7 @@ tape('destroy', function(t) {
 
   dup.destroy()
   dup.destroy() // should only work once
+  dup.end()
 })
 
 tape('destroy both', function(t) {