display: keep the cursor put, also when toggling nohelp or morespace

Also when toggling the help lines back on or the extra editing space
back off, keep the cursor near the bottom of the screen if it /was/
there, instead of centering it -- if smooth scrolling is on, that is.

This supplements the fix for https://savannah.gnu.org/bugs/?50933.

src/nano.c

@@ -1386,6 +1386,7 @@ void do_toggle(int flag)
 	case MORE_SPACE:
 	case NO_HELP:
 	    window_init();
+	    focusing=FALSE;
 	    total_refresh();
 	    break;
 	case SUSPEND: