[Qt] add more NULL pointer checks in bitcoingui

- add missing checks for clientModel and optionsModel
- small cleanups for an #ifdef on Mac
- remove an unneeded else

src/qt/bitcoingui.cpp

@@ -662,6 +662,9 @@ void BitcoinGUI::setNumConnections(int count)
 
 void BitcoinGUI::setNumBlocks(int count)
 {
+    if(!clientModel)
+        return;
+
     // Prevent orphan statusbar messages (e.g. hover Quit in main menu, wait until chain-sync starts -> garbelled text)
     statusBar()->clearMessage();
 
@@ -832,7 +835,7 @@ void BitcoinGUI::changeEvent(QEvent *e)
 #ifndef Q_OS_MAC // Ignored on Mac
     if(e->type() == QEvent::WindowStateChange)
     {
-        if(clientModel && clientModel->getOptionsModel()->getMinimizeToTray())
+        if(clientModel && clientModel->getOptionsModel() && clientModel->getOptionsModel()->getMinimizeToTray())
         {
             QWindowStateChangeEvent *wsevt = static_cast<QWindowStateChangeEvent*>(e);
             if(!(wsevt->oldState() & Qt::WindowMinimized) && isMinimized())
@@ -847,16 +850,16 @@ void BitcoinGUI::changeEvent(QEvent *e)
 
 void BitcoinGUI::closeEvent(QCloseEvent *event)
 {
-    if(clientModel)
-    {
 #ifndef Q_OS_MAC // Ignored on Mac
+    if(clientModel && clientModel->getOptionsModel())
+    {
         if(!clientModel->getOptionsModel()->getMinimizeToTray() &&
            !clientModel->getOptionsModel()->getMinimizeOnClose())
         {
             QApplication::quit();
         }
-#endif
     }
+#endif
     QMainWindow::closeEvent(event);
 }
 
@@ -917,8 +920,7 @@ bool BitcoinGUI::handlePaymentRequest(const SendCoinsRecipient& recipient)
         gotoSendCoinsPage();
         return true;
     }
-    else
-        return false;
+    return false;
 }
 
 void BitcoinGUI::setEncryptionStatus(int status)