Tweak

implementations/rust/preserves/src/value/packed/writer.rs

@@ -18,11 +18,13 @@ struct Buffers<W: io::Write> {
 
 impl<W: io::Write> io::Write for Buffers<W> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        match self.stack.last_mut() {
-            Some(bss) =>
-                bss.last_mut().expect("Internal error: PackedWriter buffer sequence underflow").write(buf),
-            None =>
-                self.base.write(buf)
+        if self.stack.is_empty() {
+            self.base.write(buf)
+        } else {
+            self.stack
+                .last_mut().unwrap()
+                .last_mut().expect("Internal error: PackedWriter buffer sequence underflow")
+                .write(buf)
         }
     }