gui: Delay interfaces::Node initialization

This is needed to allow bitcoin-gui to connect to existing node process with
-ipcconnect instead of spawning a new process. It's possible to spawn a new
bitcoin-node process without knowing the current data dir or network, but
connecting to an existing bitcoin-node requires knowing the datadir and network
first.

src/qt/bitcoin.cpp

@@ -249,7 +249,6 @@ void BitcoinApplication::createPaymentServer()
 void BitcoinApplication::createOptionsModel(bool resetSettings)
 {
     optionsModel = new OptionsModel(this, resetSettings);
-    optionsModel->setNode(node());
 }
 
 void BitcoinApplication::createWindow(const NetworkStyle *networkStyle)
@@ -264,7 +263,6 @@ void BitcoinApplication::createSplashScreen(const NetworkStyle *networkStyle)
 {
     assert(!m_splash);
     m_splash = new SplashScreen(nullptr, networkStyle);
-    m_splash->setNode(node());
     // We don't hold a direct pointer to the splash screen after creation, but the splash
     // screen will take care of deleting itself when finish() happens.
     m_splash->show();
@@ -276,6 +274,8 @@ void BitcoinApplication::setNode(interfaces::Node& node)
 {
     assert(!m_node);
     m_node = &node;
+    if (optionsModel) optionsModel->setNode(*m_node);
+    if (m_splash) m_splash->setNode(*m_node);
 }
 
 bool BitcoinApplication::baseInitialize()
@@ -465,7 +465,6 @@ int GuiMain(int argc, char* argv[])
 #endif
 
     BitcoinApplication app;
-    app.setNode(*node);
 
     /// 2. Parse command-line options. We do this after qt in order to show an error if there are problems parsing these
     // Command-line options take precedence:
@@ -599,6 +598,8 @@ int GuiMain(int argc, char* argv[])
     if (gArgs.GetBoolArg("-splash", DEFAULT_SPLASHSCREEN) && !gArgs.GetBoolArg("-min", false))
         app.createSplashScreen(networkStyle.data());
 
+    app.setNode(*node);
+
     int rv = EXIT_SUCCESS;
     try
     {