fix crash

src/metrics.js

@@ -381,7 +381,7 @@ async function pipeContainerToMap(name, statsMap) {
 
     // we used to poll before instead of a stream. but docker caches metrics internally and rate logic has to handle dups
     const [error, statsStream] = await safe(docker.getStats(name, { stream: true }));
-    if (error) return; // container stopped or missing, silently ignore
+    if (error) return null; // container stopped or missing, silently ignore
 
     statsStream.on('error', (error) => debug(error));
     statsStream.on('data', (data) => {
@@ -469,7 +469,7 @@ async function getStream(options) {
         read(/*size*/) { /* ignored, we push via interval */ },
         destroy(error, callback) {
             clearInterval(intervalId);
-            containerStreamPromises.forEach(cs => { if (cs.status === 'fulfilled') cs.value.destroy(error); });
+            containerStreamPromises.forEach(cs => { if (cs.status === 'fulfilled' && cs.value) cs.value.destroy(error); });
             callback(error);
         }
     });