[APM] Fix agent marks

x-pack/plugins/apm/public/components/app/TransactionDetails/Transaction/WaterfallContainer/get_agent_marks.test.ts

@@ -8,7 +8,7 @@ import { Transaction } from 'x-pack/plugins/apm/typings/Transaction';
 import { getAgentMarks } from './get_agent_marks';
 
 describe('getAgentMarks', () => {
-  it('should sort the marks', () => {
+  it('should sort the marks by time', () => {
     const transaction: Transaction = {
       transaction: {
         marks: {
@@ -33,4 +33,11 @@ describe('getAgentMarks', () => {
     } as any;
     expect(getAgentMarks(transaction)).toEqual([]);
   });
+
+  it('should return empty array if agent marks are missing', () => {
+    const transaction: Transaction = {
+      transaction: { marks: {} }
+    } as any;
+    expect(getAgentMarks(transaction)).toEqual([]);
+  });
 });

x-pack/plugins/apm/public/components/app/TransactionDetails/Transaction/WaterfallContainer/get_agent_marks.ts

@@ -13,7 +13,7 @@ export interface AgentMark {
 }
 
 export function getAgentMarks(transaction: Transaction): AgentMark[] {
-  if (!transaction.transaction.marks) {
+  if (!(transaction.transaction.marks && transaction.transaction.marks.agent)) {
     return [];
   }
 

x-pack/plugins/apm/typings/Transaction.ts

@@ -37,7 +37,7 @@ interface Context {
 }
 
 interface Marks {
-  agent: {
+  agent?: {
     [name: string]: number;
   };
 }