Prevent segfault when editing a textarea field with vi

add fix for segfault that can occur when editing a textarea field
with vi, and returning to w3m (it seems to happen if the terminal
is not writable, as when using w3m after 'su - some_user')

Origin: https://build.opensuse.org/package/view_file/openSUSE:Factory/w3m/w3m-0.4.1-textarea-segfault.dif?expand=1

terms.c

@@ -637,7 +637,8 @@ reset_tty(void)
     writestr(T_se);		/* reset terminal */
     flush_tty();
     TerminalSet(tty, &d_ioval);
-    close_tty();
+    if (tty != 2)
+        close_tty();
 }
 
 static MySignalHandler