Fix `set` for Firefox & Safari (don't set non-own properties in for..in loop)

platform/firefox/vapi-background.js

@@ -195,6 +195,9 @@ vAPI.storage = {
         var key, values = [], placeholders = [];
 
         for ( key in details ) {
+            if ( !details.hasOwnProperty(key) ) {
+                continue;
+            }
             values.push(key);
             values.push(JSON.stringify(details[key]));
             placeholders.push('?, ?');

platform/safari/vapi-background.js

@@ -126,6 +126,9 @@ vAPI.storage = {
 
     set: function(details, callback) {
         for ( var key in details ) {
+            if ( !details.hasOwnProperty(key) ) {
+                continue;
+            }
             this._storage.setItem(key, JSON.stringify(details[key]));
         }