hal/ui: add empty_create to Ui Hal

diff --git a/src/rust/bitbox-hal/src/ui.rs b/src/rust/bitbox-hal/src/ui.rs
index f922a01..ecb55b9 100644
--- a/src/rust/bitbox-hal/src/ui.rs
+++ b/src/rust/bitbox-hal/src/ui.rs
@@ -65,9 +65,12 @@ pub trait Progress {
     fn set(&mut self, progress: f32);
 }
 
+pub trait Empty {}
+
 #[allow(async_fn_in_trait)]
 pub trait Ui {
     type Progress: Progress;
+    type Empty: Empty;
 
     /// Returns `Ok(())` if the user accepts, `Err(UserAbort)` if the user rejects.
     async fn confirm(&mut self, params: &ConfirmParams<'_>) -> Result<(), UserAbort>;
@@ -91,6 +94,8 @@ pub trait Ui {
 
     fn progress_create(&mut self, title: &str) -> Self::Progress;
 
+    fn empty_create(&mut self) -> Self::Empty;
+
     /// If `can_cancel` is `Yes`, the workflow can be cancelled.
     /// If it is `No`, the result is always `Ok(())`.
     /// If `preset` is not empty, it must be part of `params.wordlist` and will be pre-entered.
diff --git a/src/rust/bitbox02-rust/src/hal/testing/ui.rs b/src/rust/bitbox02-rust/src/hal/testing/ui.rs
index 0a11bc9..db58a03 100644
--- a/src/rust/bitbox02-rust/src/hal/testing/ui.rs
+++ b/src/rust/bitbox02-rust/src/hal/testing/ui.rs
@@ -2,7 +2,7 @@
 
 use crate::hal::Ui;
 use crate::hal::ui::{
-    CanCancel, ConfirmParams, EnterStringParams, Progress, TrinaryChoice, UserAbort,
+    CanCancel, ConfirmParams, Empty, EnterStringParams, Progress, TrinaryChoice, UserAbort,
 };
 
 use alloc::boxed::Box;
@@ -63,13 +63,22 @@ impl Progress for NoopProgress {
     fn set(&mut self, _progress: f32) {}
 }
 
+pub struct NoopEmpty;
+
+impl Empty for NoopEmpty {}
+
 impl Ui for TestingUi<'_> {
     type Progress = NoopProgress;
+    type Empty = NoopEmpty;
 
     fn progress_create(&mut self, _title: &str) -> Self::Progress {
         NoopProgress
     }
 
+    fn empty_create(&mut self) -> Self::Empty {
+        NoopEmpty
+    }
+
     async fn confirm(&mut self, params: &ConfirmParams<'_>) -> Result<(), UserAbort> {
         self.screens.push(Screen::Confirm {
             title: params.title.into(),
diff --git a/src/rust/bitbox02-rust/src/hww/api/bitcoin/signtx.rs b/src/rust/bitbox02-rust/src/hww/api/bitcoin/signtx.rs
index 85c0f8e..858e5bf 100644
--- a/src/rust/bitbox02-rust/src/hww/api/bitcoin/signtx.rs
+++ b/src/rust/bitbox02-rust/src/hww/api/bitcoin/signtx.rs
@@ -835,11 +835,7 @@ async fn _process(
             // Stop rendering inputs progress update.
             drop(progress_component.take());
 
-            empty_component = {
-                let mut c = bitbox02::ui::empty_create();
-                c.screen_stack_push();
-                Some(c)
-            };
+            empty_component = Some(hal.ui().empty_create());
         }
 
         let output_type = pb::BtcOutputType::try_from(tx_output.r#type)?;
diff --git a/src/rust/bitbox02-rust/src/hww/api/ethereum/sign_typed_msg.rs b/src/rust/bitbox02-rust/src/hww/api/ethereum/sign_typed_msg.rs
index 3b82576..b42b753 100644
--- a/src/rust/bitbox02-rust/src/hww/api/ethereum/sign_typed_msg.rs
+++ b/src/rust/bitbox02-rust/src/hww/api/ethereum/sign_typed_msg.rs
@@ -520,8 +520,7 @@ pub async fn process(
     // Base component on the screen stack during signing, which is shown while the device is waiting
     // for the next signing api call. Without this, the 'See the BitBoxApp' waiting screen would
     // flicker in between user confirmations.
-    let mut empty_component = bitbox02::ui::empty_create();
-    empty_component.screen_stack_push();
+    let _empty_component = hal.ui().empty_create();
 
     // Verify address. We don't need the actual result, but we have to propagate validation or user
     // abort errors.
diff --git a/src/rust/bitbox02/src/hal/ui.rs b/src/rust/bitbox02/src/hal/ui.rs
index a5ddcbb..93159cb 100644
--- a/src/rust/bitbox02/src/hal/ui.rs
+++ b/src/rust/bitbox02/src/hal/ui.rs
@@ -4,8 +4,8 @@ use alloc::string::String;
 
 use bitbox_hal::Ui;
 use bitbox_hal::ui::{
-    CanCancel, ConfirmParams, EnterStringParams, Font, Progress as HalProgress, TrinaryChoice,
-    UserAbort,
+    CanCancel, ConfirmParams, Empty as HalEmpty, EnterStringParams, Font, Progress as HalProgress,
+    TrinaryChoice, UserAbort,
 };
 
 pub struct BitBox02Ui;
@@ -20,6 +20,12 @@ impl HalProgress for BitBox02Progress {
     }
 }
 
+pub struct BitBox02Empty {
+    _component: crate::ui::Component,
+}
+
+impl HalEmpty for BitBox02Empty {}
+
 fn to_bitbox02_font(font: Font) -> crate::ui::Font {
     match font {
         Font::Default => crate::ui::Font::Default,
@@ -67,6 +73,7 @@ fn to_hal_trinary_choice(choice: crate::ui::TrinaryChoice) -> TrinaryChoice {
 
 impl Ui for BitBox02Ui {
     type Progress = BitBox02Progress;
+    type Empty = BitBox02Empty;
 
     fn progress_create(&mut self, title: &str) -> Self::Progress {
         let mut component = crate::ui::progress_create(title);
@@ -74,6 +81,14 @@ impl Ui for BitBox02Ui {
         BitBox02Progress { component }
     }
 
+    fn empty_create(&mut self) -> Self::Empty {
+        let mut component = crate::ui::empty_create();
+        component.screen_stack_push();
+        BitBox02Empty {
+            _component: component,
+        }
+    }
+
     #[inline(always)]
     async fn confirm(&mut self, params: &ConfirmParams<'_>) -> Result<(), UserAbort> {
         let params = to_bitbox02_confirm_params(params);