remove panic from Debug of StreamRef is mutex is poisoned

src/proto/streams/streams.rs

@@ -734,12 +734,20 @@ where
     P: Peer,
 {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        let me = self.inner.lock().unwrap();
+        match self.inner.lock() {
+            Ok(me) => {
                 let stream = &me.store[self.key];
                 fmt.debug_struct("StreamRef")
                     .field("stream_id", &stream.id)
                     .field("ref_count", &stream.ref_count)
                     .finish()
+            },
+            Err(_poisoned) => {
+                fmt.debug_struct("StreamRef")
+                    .field("inner", &"<Poisoned>")
+                    .finish()
+            }
+        }
     }
 }