Remove unwraps in alloc error handler

src/lang_items.rs

diff --git a/src/lang_items.rs b/src/lang_items.rs
index 1d61e4c..197de47 100644
--- a/src/lang_items.rs
+++ b/src/lang_items.rs
@@ -47,18 +47,22 @@
 
     // Flash all LEDs (if available).
     executor::block_on(async {
-        let context = timer::DriverContext::create().ok().unwrap();
-        let mut driver = context.create_timer_driver_unsafe();
-        let timer_driver = driver.activate().ok().unwrap();
+        let context = timer::DriverContext::create().ok();
+        let mut driver = context.as_ref().map(|c| c.create_timer_driver_unsafe());
+        let timer_driver = driver.as_mut().and_then(|d| d.activate().ok());
         loop {
             for led in led::all() {
                 let _ = led.on();
             }
-            let _ = timer_driver.sleep(Duration::from_ms(100)).await;
+            if let Some(ref timer_driver) = timer_driver {
+                let _ = timer_driver.sleep(Duration::from_ms(100)).await;
+            }
             for led in led::all() {
                 let _ = led.off();
             }
-            let _ = timer_driver.sleep(Duration::from_ms(100)).await;
+            if let Some(ref timer_driver) = timer_driver {
+                let _ = timer_driver.sleep(Duration::from_ms(100)).await;
+            }
         }
     });
     // Never type is not supported for T in Future