patch 9.0.0665: setting 'cmdheight' has no effect if last window was resized

Problem:    Setting 'cmdheight' has no effect if last window was resized.
Solution:   Do apply 'cmdheight' when told to.  Use the frame height instead
            of the cmdline_row.  (closes #11286)
diff --git a/src/option.c b/src/option.c
index 7d6b954..1b8c3ea 100644
--- a/src/option.c
+++ b/src/option.c
@@ -3577,11 +3577,12 @@
 
 	// Only compute the new window layout when startup has been
 	// completed. Otherwise the frame sizes may be wrong.
-	if (p_ch != old_value && full_screen
+	if ((p_ch != old_value || topframe->fr_height != Rows - p_ch)
+		&& full_screen
 #ifdef FEAT_GUI
 		&& !gui.starting
 #endif
-	   )
+		       )
 	    command_height();
     }