Don't panic in WorkController::drop

src/state.rs

@@ -220,7 +220,7 @@ impl Drop for State {
             use nix::sys::wait::{waitpid, WaitPidFlag};
             /* Try wait, we don't want to block */
             if let Err(e) = waitpid(child_pid, Some(WaitPidFlag::WNOHANG)) {
-                eprintln!("Failed to wait on subprocess {}: {}", child_pid, e);
+                debug!("Failed to wait on subprocess {}: {}", child_pid, e);
             }
         }
     }

src/workers.rs

@@ -64,8 +64,10 @@ pub struct WorkController {
 
 impl Drop for WorkController {
     fn drop(&mut self) {
-        for _ in 0..self.threads.lock().unwrap().len() {
-            self.thread_end_tx.send(true).unwrap();
+        if let Ok(lock) = self.threads.lock() {
+            for _ in 0..lock.len() {
+                let _ = self.thread_end_tx.send(true);
+            }
         }
     }
 }