patch 8.2.0632: crash when using Haiku

Problem:    Crash when using Haiku.
Solution:   Lock the screen. (closes #5975, closes #5973)
diff --git a/src/screen.c b/src/screen.c
index d73e7c6..845c5b2 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -3881,6 +3881,10 @@
 	clip_scroll_selection(line_count);
 #endif
 
+#ifdef FEAT_GUI_HAIKU
+    vim_lock_screen();
+#endif
+
 #ifdef FEAT_GUI
     // Don't update the GUI cursor here, ScreenLines[] is invalid until the
     // scrolling is actually carried out.