From 5bc00b220f1228391c765febaa9e62aec43e240f Mon Sep 17 00:00:00 2001
From: "Joakim L. Gilje" <jgilje@jgilje.net>
Date: Wed, 8 Dec 2021 14:47:09 +0100
Subject: [PATCH] handle early ui_msgbox_header() calls before main_window has
 been created

---
 src/qt/qt_ui.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/qt/qt_ui.cpp b/src/qt/qt_ui.cpp
index 4af7423cc..a62a37de9 100644
--- a/src/qt/qt_ui.cpp
+++ b/src/qt/qt_ui.cpp
@@ -2,6 +2,7 @@
 
 #include <QDebug>
 #include <QThread>
+#include <QMessageBox>
 
 #include <QStatusBar>
 
@@ -60,7 +61,13 @@ int	ui_msgbox_header(int flags, void *header, void* message) {
     auto hdr = QString::fromWCharArray(reinterpret_cast<const wchar_t*>(header));
     auto msg = QString::fromWCharArray(reinterpret_cast<const wchar_t*>(message));
 
-    main_window->showMessage(hdr, msg);
+    // any error in early init
+    if (main_window == nullptr) {
+        QMessageBox::critical(nullptr, hdr, msg);
+    } else {
+        // else scope it to main_window
+        main_window->showMessage(hdr, msg);
+    }
     return 0;
 }