tape: only query volume stats if we can read MAM

src/tape/drive/linux_tape.rs

@@ -238,7 +238,6 @@ impl LinuxTapeHandle {
                 status.manufactured = Some(usage.manufactured);
                 status.bytes_read = Some(usage.bytes_read);
                 status.bytes_written = Some(usage.bytes_written);
-            }
 
                 if let Ok(volume_stats) = self.volume_statistics() {
 
@@ -250,6 +249,7 @@ impl LinuxTapeHandle {
                     status.volume_mounts = Some(volume_stats.volume_mounts);
                 }
             }
+        }
 
         Ok(status)
     }