fix(logstream): clear logstream reference on cleanup

Set the logstream property to undefined during cleanup to prevent
potential memory leaks or stale references. Also, adjust the callback
invocation in modify for clearer structure while keeping the same behavior.

Author: rohitpaulk

app/modifiers/logstream-did-update.ts

@@ -17,6 +17,7 @@ interface Signature {
 function cleanup(instance: LogstreamDidUpdateModifier) {
   if (instance.logstream) {
     instance.logstream.unsubscribe();
+    instance.logstream = undefined;
   }
 }
 
@@ -34,7 +35,10 @@ export default class LogstreamDidUpdateModifier extends Modifier<Signature> {
   modify(_element: HTMLElement, [callback, logstreamId]: Signature['Args']['Positional']) {
     cleanup(this);
 
-    this.logstream = new Logstream(logstreamId, this.actionCableConsumer, this.store, () => callback(this.logstream!));
+    this.logstream = new Logstream(logstreamId, this.actionCableConsumer, this.store, () => {
+      callback(this.logstream!);
+    });
+
     this.logstream.subscribe();
   }
 }