Enable reportError tests in ShadowRealm

reportError seems to be minimally tested. ShadowRealm doesn't have the
location exposed, so just assume it will be blank. This may need to be
changed depending on what browsers do. It is not specified what the value
should be in https://html.spec.whatwg.org/#extract-error:

  "Set _attributes_[message], _attributes_[filename],
  _attributes_[lineno], and _attributes_[colno] to implementation-defined
  values derived from _exception_.

  NOTE: Browsers implement behavior not specified here or in the
  JavaScript specification to gather values which are helpful, including
  in unusual cases (e.g., `eval`). In the future, this might be specified
  in greater detail.

This seems like exactly such an unusual case.

html/webappapis/scripting/reporterror.any.js

@@ -1,3 +1,5 @@
+// META: global=window,dedicatedworker,shadowrealm
+
 setup({ allow_uncaught_exception:true });
 
 [
@@ -9,7 +11,7 @@ setup({ allow_uncaught_exception:true });
     let happened = false;
     self.addEventListener("error", t.step_func(e => {
       assert_true(e.message !== "");
-      assert_equals(e.filename, new URL("reporterror.any.js", location.href).href);
+      assert_equals(e.filename, location ? new URL("reporterror.any.js", location.href).href : "");
       assert_greater_than(e.lineno, 0);
       assert_greater_than(e.colno, 0);
       assert_equals(e.error, throwable);