More direct check for zero-length duration

Author: joto

src/thread-pool.cpp

@@ -16,7 +16,7 @@ std::chrono::milliseconds task_result_t::wait()
 
         // Make sure the result is not 0 so it is different than
         // "no result yet".
-        if (m_result.count() == 0) {
+        if (m_result == std::chrono::milliseconds::zero()) {
             ++m_result;
         }
     }