lib: fix segfault with --without-intl

Node.js segfaults when build with `--without-intl` due to an oversight
in d13cdd9. This fixes the issue.

PR-URL: #21589
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/internal/per_context.js

@@ -4,7 +4,7 @@
 
 (function(global) {
   // https://github.com/nodejs/node/issues/14909
-  delete global.Intl.v8BreakIterator;
+  if (global.Intl) delete global.Intl.v8BreakIterator;
 
   // https://github.com/nodejs/node/issues/21219
   // Adds Atomics.notify and warns on first usage of Atomics.wake