StyledEdit: Fix #10349.

Override QuitRequested in FindWindow to notify the parent edit window of the
find window's demise so it can reset its corresponding pointer. Otherwise the
latter will potentially access the invalid pointer in question on subsequent
find requests, leading to potential crashes.

src/apps/stylededit/Constants.h

@@ -43,6 +43,7 @@ const uint32 MSG_SEARCH					= 'msea';
 const uint32 MSG_REPLACE				= 'msre';
 const uint32 MSG_REPLACE_ALL			= 'mrea';
 const uint32 MSG_HIDE_WINDOW			= 'mhdw';
+const uint32 MSG_FIND_WINDOW_QUIT		= 'mfwq';
 
 // "Font"-menu
 const uint32 FONT_SIZE					= 'FMsi';

src/apps/stylededit/FindWindow.cpp

@@ -110,6 +110,16 @@ FindWindow::DispatchMessage(BMessage* message, BHandler* handler)
 }
 
 
+bool
+FindWindow::QuitRequested()
+{
+	BMessenger messenger(fHandler);
+	messenger.SendMessage(MSG_FIND_WINDOW_QUIT);
+
+	return true;
+}
+
+
 void
 FindWindow::Show()
 {

src/apps/stylededit/FindWindow.h

@@ -26,6 +26,7 @@ class FindWindow : public BWindow {
 
 		virtual void	MessageReceived(BMessage* message);
 		virtual void	DispatchMessage(BMessage* message, BHandler* handler);
+		virtual	bool	QuitRequested();
 		virtual void	Show();
 
 	private:

src/apps/stylededit/StyledEditWindow.cpp

@@ -254,6 +254,11 @@ StyledEditWindow::MessageReceived(BMessage* message)
 				fFindWindow->Activate();
 			break;
 		}
+		case MSG_FIND_WINDOW_QUIT:
+		{
+			fFindWindow = NULL;
+			break;
+		}
 		case MSG_SEARCH:
 			message->FindString("findtext", &fStringToFind);
 			fFindAgainItem->SetEnabled(true);