subs: fix incorrect stream_info re-initialization.

Using [] doesn't cause incorrect behavior, but it's a mismatch with
how stream_info is initially declared and gives you a confusing
representation at the console.

(imported from commit c03d9e6a29ff990659f41ee478f631a019a5ac25)

zephyr/static/js/subs.js

@@ -474,7 +474,7 @@ exports.reload_subscriptions = function (opts) {
     }
 
     if (opts.clear_first) {
-        stream_info = [];
+        stream_info = {};
         ui.remove_all_narrow_filters();
     }