Merge 0.5.7 (#88)

* Add null checks

* update label

* capitalization and update translations

* v0.5.7

* Don't show error on cancel

src/rpc.h

@@ -38,7 +38,7 @@ public:
 
     void refreshAddresses();    
     
-    void checkForUpdate();
+    void checkForUpdate(bool silent = true);
     void refreshZECPrice();
     void getZboardTopics(std::function<void(QMap<QString, QString>)> cb);