Ensure listener is cleaned up

Also fixed bug when validating a tx with no value.

app/scripts/background.js

@@ -86,6 +86,7 @@ function setupControllerConnection (stream) {
   stream.pipe(dnode).pipe(stream)
   dnode.on('remote', (remote) => {
     // push updates to popup
+    controller.ethStore.removeListener('update', controller.sendUpdate.bind(controller))
     controller.ethStore.on('update', controller.sendUpdate.bind(controller))
     controller.listeners.push(remote)
     idStore.on('update', controller.sendUpdate.bind(controller))

app/scripts/lib/listener-manager.js

@@ -0,0 +1,25 @@
+module.exports = class ListenerManager {
+
+  constructor() {
+    this.cleaners = {}
+  }
+
+  setup (name) {
+    if (!(name in this.cleaners)) {
+      this.cleaners[name] = []
+    }
+  }
+
+  addCleanup (name, cleaner) {
+    this.setup(name)
+  }
+
+  cleanupOldListeners (name) {
+    this.setup(name)
+    this.cleaners[name].forEach((cleaner) => {
+      cleaner()
+    })
+    this.cleaners[name] = []
+  }
+
+}

app/scripts/metamask-controller.js

@@ -220,7 +220,7 @@ module.exports = class MetamaskController {
   }
 
   enforceTxValidations (txParams) {
-    if (txParams.value.indexOf('-') === 0) {
+    if (('value' in txParams) && txParams.value.indexOf('-') === 0) {
       const msg = `Invalid transaction value of ${txParams.value} not a positive number.`
       return new Error(msg)
     }