Noticed this while reviewing #13529, but it's also in master @ 5ba77df. On macOS 10.13.6:

<img width="209" alt="schermafbeelding 2018-08-01 om 16 22 09" src="https://user-images.githubusercontent.com/10217/43527498-0f571db4-95a7-11e8-8d90-7863947a7689.png">


<img width="178" alt="schermafbeelding 2018-08-01 om 16 12 51" src="https://user-images.githubusercontent.com/10217/43526994-c9a515ec-95a5-11e8-96b8-9e2513e9aac5.png">

* `Show` in the action menu doesn't work if the app was hidden by `Command + H`, it does work when hidden through this menu
* send and receive don't unhide the window when opened for the action menu. It does navigate to the right tab. The other actions do work (sign, verify & debug window)

Clicking "Toon" (= macOS native show) does work, suggesting the GUI uses some non-native method of hiding.
std::unique_ptr<interfaces::Handler> m_handler_message_box;
    std::unique_ptr<interfaces::Handler> m_handler_question;
    ClientModel* clientModel = nullptr;
    WalletFrame* walletFrame = nullptr;
    UnitDisplayStatusBarControl* unitDisplayControl = nullptr;
    QLabel* labelWalletEncryptionIcon = nullptr;
    QLabel* labelWalletHDStatusIcon = nullptr;
    GUIUtil::ClickableLabel* labelProxyIcon = nullptr;
    GUIUtil::ClickableLabel* connectionsControl = nullptr;
    GUIUtil::ClickableLabel* labelBlocksIcon = nullptr;
    QLabel* progressBarLabel = nullptr;
    GUIUtil::ClickableProgressBar* progressBar = nullptr;
    QProgressDialog* progressDialog = nullptr;
    QMenuBar* appMenuBar = nullptr;
    QToolBar* appToolBar = nullptr;
    QAction* overviewAction = nullptr;
    QAction* historyAction = nullptr;
    QAction* quitAction = nullptr;
    QAction* sendCoinsAction = nullptr;
    QAction* sendCoinsMenuAction = nullptr;
    QAction* usedSendingAddressesAction = nullptr;
    QAction* usedReceivingAddressesAction = nullptr;
    QAction* signMessageAction = nullptr;
    QAction* verifyMessageAction = nullptr;
    QAction* aboutAction = nullptr;
    QAction* receiveCoinsAction = nullptr;
    QAction* receiveCoinsMenuAction = nullptr;
    QAction* optionsAction = nullptr;
    QAction* toggleHideAction = nullptr;
    QAction* encryptWalletAction = nullptr;