NetworkSettings: Don't assert when there are no network adapters

NetworkSettings normally filters out `loop` when populating its list of
adapters. However, when checking if there aren't any adapters it did
not take this into account. This causes it to crash later when trying
to set the selected index of an empty combo box.

This moves the check for no adapters to after filtering the list, so
that shows the error message and exits.

Userland/Applications/NetworkSettings/NetworkSettingsWidget.cpp

@@ -77,12 +77,6 @@ ErrorOr<void> NetworkSettingsWidget::setup()
     JsonParser parser(data);
     JsonValue proc_net_adapters_json = TRY(parser.parse());
 
-    // FIXME: This should be done before creating a window.
-    if (proc_net_adapters_json.as_array().is_empty()) {
-        GUI::MessageBox::show_error(window(), "No network adapters found!"sv);
-        ::exit(1);
-    }
-
     size_t selected_adapter_index = 0;
     size_t index = 0;
     proc_net_adapters_json.as_array().for_each([&](auto& value) {
@@ -109,6 +103,12 @@ ErrorOr<void> NetworkSettingsWidget::setup()
         index++;
     });
 
+    // FIXME: This should be done before creating a window.
+    if (m_adapter_names.is_empty()) {
+        GUI::MessageBox::show_error(window(), "No network adapters found!"sv);
+        ::exit(1);
+    }
+
     m_adapters_combobox->set_model(TRY(GUI::ItemListModel<DeprecatedString>::try_create(m_adapter_names)));
     m_adapters_combobox->on_change = [this](DeprecatedString const& text, GUI::ModelIndex const&) {
         on_switch_adapter(text);