Fix display flickering

src/main.rs

@@ -134,7 +134,7 @@ where
     )
     .draw(display)?;
 
-    display.flush()
+    Ok(())
 }
 
 #[entry]
@@ -297,6 +297,10 @@ fn main() -> ! {
             if let Err(err) = display_text(&mut display, state_str, Baseline::Top) {
                 let _ = println_serial(&mut serial, stringify_display_error(err));
             }
+
+            if let Err(err) = display.flush() {
+                let _ = println_serial(&mut serial, stringify_display_error(err));
+            }
         }
 
         if let Some(temperature) = current_temperature {