lntest: assert shutdown via logs only if log handle is present

Ensure shutdown assertions through log inspection are only performed
when the harness node has an active log file handle. This avoids
errors during shutdown when log file output is disabled.

lntest/node/harness_node.go

@@ -671,14 +671,18 @@ func (hn *HarnessNode) WaitForProcessExit() error {
 		hn.printErrf("timeout waiting for process to exit")
 	}
 
-	// Make sure log file is closed and renamed if necessary.
+	// If the node has an open log file handle, inspect the log file
-	filename := finalizeLogfile(hn)
+	// to verify that the node shut down correctly.
+	if hn.logFile != nil {
+		// Make sure log file is closed and renamed if necessary.
+		filename := finalizeLogfile(hn)
 
-	// Assert the node has shut down from the log file.
+		// Assert the node has shut down from the log file.
-	err1 := assertNodeShutdown(filename)
+		err1 := assertNodeShutdown(filename)
-	if err1 != nil {
+		if err1 != nil {
-		return fmt.Errorf("[%s]: assert shutdown failed in log[%s]: %w",
+			return fmt.Errorf("[%s]: assert shutdown failed in "+
-			hn.Name(), filename, err1)
+				"log[%s]: %w", hn.Name(), filename, err1)
+		}
 	}
 
 	// Rename the etcd.log file if the node was running on embedded etcd.