Prevent unhandled exception when streams are closing

and the session is still busy

Fixes #36

source/agent.js

@@ -70,13 +70,13 @@ const addSession = (where, name, session) => {
 };
 
 const getSessions = (where, name, normalizedOrigin) => {
-	if (Reflect.has(where, name)) {
-		return where[name].filter(session => {
-			return !session.closed && !session.destroyed && session[kOriginSet].includes(normalizedOrigin);
-		});
+	if (!Reflect.has(where, name)) {
+		return [];
 	}
 
-	return [];
+	return where[name].filter(session => {
+		return !session.closed && !session.destroyed && session[kOriginSet].includes(normalizedOrigin);
+	});
 };
 
 // See https://tools.ietf.org/html/rfc8336
@@ -108,6 +108,10 @@ const closeCoveredSessions = (where, name, session) => {
 
 // This is basically inverted `closeCoveredSessions(...)`.
 const closeSessionIfCovered = (where, name, coveredSession) => {
+	if (!Reflect.has(where, name)) {
+		return;
+	}
+
 	for (const session of where[name]) {
 		if (
 			coveredSession[kOriginSet].length < session[kOriginSet].length &&

test/agent.js

@@ -462,6 +462,25 @@ test('sessions can be manually overloaded', singleRequestWrapper, async (t, serv
 	agent.destroy();
 });
 
+test('sessions can be manually overloaded #2', singleRequestWrapper, async (t, server) => {
+	server.get('/', (request, response) => {
+		response.end();
+	});
+
+	const agent = new Agent();
+
+	const session = await agent.getSession(server.url);
+	const requests = [session.request(), session.request()];
+
+	requests[0].end();
+
+	await pEvent(requests[0], 'close');
+
+	t.pass();
+
+	agent.destroy();
+});
+
 test('`.settings` property', wrapper, async (t, server) => {
 	const agent = new Agent();
 	agent.settings.maxHeaderListSize = 100;