patch 9.0.0670: no space for command line when there is a tabline

Problem:    No space for command line when there is a tabline.
Solution:   Correct computation of where the command line should be.
            (closes #11295)
diff --git a/src/option.c b/src/option.c
index 1b8c3ea..3cd1d40 100644
--- a/src/option.c
+++ b/src/option.c
@@ -3577,7 +3577,8 @@
 
 	// Only compute the new window layout when startup has been
 	// completed. Otherwise the frame sizes may be wrong.
-	if ((p_ch != old_value || topframe->fr_height != Rows - p_ch)
+	if ((p_ch != old_value
+		      || tabline_height() + topframe->fr_height != Rows - p_ch)
 		&& full_screen
 #ifdef FEAT_GUI
 		&& !gui.starting