node tests: Use set_find_results in stream_edit test.

frontend_tests/zjsunit/zjquery_element.js

@@ -202,6 +202,11 @@ function FakeElement(selector, opts) {
             return self;
         },
         set_find_results(find_selector, jquery_object) {
+            if (jquery_object === undefined) {
+                throw new Error(
+                    "Please make the 'find result' be something like $.create('unused')",
+                );
+            }
             find_results.set(find_selector, jquery_object);
         },
         set_height(fake_height) {