Update NBGL spinner

Author: yogh333

ledger_device_sdk/src/nbgl/nbgl_spinner.rs

@@ -7,15 +7,15 @@ use alloc::ffi::CString;
 /// 800 ms, provided the IO event loop is running to process TickerEvents.
 #[derive(Debug, Default)]
 pub struct NbglSpinner {
-    text: [Option<CString>; 2],
+    text: [CString; 2],
     write_idx: usize,
     read_idx: usize,
 }
 
 impl NbglSpinner {
     pub fn new() -> NbglSpinner {
         NbglSpinner {
-            text: [None, None],
+            text: [CString::default(), CString::default()],
             write_idx: 0,
             read_idx: 0,
         }
@@ -24,13 +24,11 @@ impl NbglSpinner {
     /// Shows the spinner with the current text.
     /// Every call make the spinner "turn" to the next text.
     pub fn show(&mut self, text: &str) {
-        self.text[self.write_idx] = Some(CString::new(text).unwrap());
+        self.text[self.write_idx] = CString::new(text).unwrap();
         self.read_idx = self.write_idx;
         self.write_idx = (self.write_idx + 1) % 2;
         unsafe {
-            nbgl_useCaseSpinner(
-                self.text[self.read_idx].as_ref().unwrap().as_ptr() as *const c_char
-            );
+            nbgl_useCaseSpinner(self.text[self.read_idx].as_ptr() as *const c_char);
         }
     }
 }