[FL-2226] BadUSB, U2F: missing assets error (#979)

* badusb, u2f: showing error screen if assets are missing
* BadUsb: remove dead code
* U2F: remove dead code

Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

applications/bad_usb/scenes/bad_usb_scene_error.c

@@ -0,0 +1,53 @@
+#include "../bad_usb_app_i.h"
+
+typedef enum {
+    SubghzCustomEventErrorBack,
+} BadUsbCustomEvent;
+
+static void
+    bad_usb_scene_error_event_callback(GuiButtonType result, InputType type, void* context) {
+    furi_assert(context);
+    BadUsbApp* app = context;
+
+    if((result == GuiButtonTypeLeft) && (type == InputTypeShort)) {
+        view_dispatcher_send_custom_event(app->view_dispatcher, SubghzCustomEventErrorBack);
+    }
+}
+
+void bad_usb_scene_error_on_enter(void* context) {
+    BadUsbApp* app = context;
+
+    widget_add_icon_element(app->widget, 0, 0, &I_SDQuestion_35x43);
+
+    widget_add_string_multiline_element(
+        app->widget,
+        81,
+        4,
+        AlignCenter,
+        AlignTop,
+        FontSecondary,
+        "No SD card or\napp data found.\nThis app will not\nwork without\nrequired files.");
+
+    widget_add_button_element(
+        app->widget, GuiButtonTypeLeft, "Back", bad_usb_scene_error_event_callback, app);
+
+    view_dispatcher_switch_to_view(app->view_dispatcher, BadUsbAppViewError);
+}
+
+bool bad_usb_scene_error_on_event(void* context, SceneManagerEvent event) {
+    BadUsbApp* app = context;
+    bool consumed = false;
+
+    if(event.type == SceneManagerEventTypeCustom) {
+        if(event.event == SubghzCustomEventErrorBack) {
+            view_dispatcher_stop(app->view_dispatcher);
+            consumed = true;
+        }
+    }
+    return consumed;
+}
+
+void bad_usb_scene_error_on_exit(void* context) {
+    BadUsbApp* app = context;
+    widget_clear(app->widget);
+}