Fix internalDestroy causing node crash

When the ForwardClose times out, CIPConnectionLayer.js calls this.destroy('Forward Close error'). That goes into internalDestroy, which iterates pending callbacks. One of them is the very same disconnect callback. Inside that callback, this.destroy(...) is called again, and because clear() happens after forEach, the map still contains the same callback, so it re-enters infinitely.
internalDestroy now clears the callback map before invoking, breaking the recursion.

Author: diogo24m

src/layers/Layer.js

@@ -24,8 +24,11 @@ function internalDestroy(layer, error) {
   layer.__contextToCallbackTimeouts.forEach((handle) => clearTimeout(handle));
   layer.__contextToCallbackTimeouts.clear(); // eslint-disable-line no-underscore-dangle
 
-  layer.__contextToCallback.forEach((cb) => cb(error)); // eslint-disable-line no-underscore-dangle
+  const callbacks = Array.from(layer.__contextToCallback.values());
   layer.__contextToCallback.clear(); // eslint-disable-line no-underscore-dangle
+  for (const cb of callbacks) {
+    try { cb(error); } catch (e) { /* swallow — destroy must not throw */ }
+  }
 
   layer.__idContext.clear(); // eslint-disable-line