#14899: Hide main windows on close instead of deleting them

WA_DeleteOnClose left RiuMainWindow::instance() and RiuPlotMainWindow::instance() null after the user closed a window, so any unguarded use crashed. Keep both windows alive for the application lifetime and rebuild their views when a closed window is shown again.

Fixes #14899.

ApplicationLibCode/UserInterface/RiuMainWindowBase.cpp

@@ -93,6 +93,7 @@ RiuMainWindowBase::RiuMainWindowBase()
     , m_blockSubWindowProjectTreeSelection( false )
     , m_hasBeenVisible( false )
     , m_isBeingDestroyed( false )
+    , m_hasBeenClosed( false )
     , m_windowMenu( nullptr )
 {
     ads::CDockManager::setAutoHideConfigFlags( ads::CDockManager::DefaultAutoHideConfig );
@@ -283,6 +284,9 @@ void RiuMainWindowBase::saveWinGeoAndDockToolBarLayout()
     // https://github.com/OPM/ResInsight/issues/9935
     if ( !m_hasBeenVisible ) return;
 
+    // The views were removed from docking when the window was closed, and the state was saved before that
+    if ( m_hasBeenClosed ) return;
+
     // Company and appname set through QCoreApplication
     QSettings settings;
 
@@ -863,9 +867,27 @@ void RiuMainWindowBase::closeEvent( QCloseEvent* event )
         view->removeWindowFromDock();
     }
 
+    m_hasBeenClosed = true;
+
     QMainWindow::closeEvent( event );
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+bool RiuMainWindowBase::hasBeenClosed() const
+{
+    return m_hasBeenClosed;
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+void RiuMainWindowBase::clearClosedState()
+{
+    m_hasBeenClosed = false;
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------