inspector: fix crash on exception

Fixes: nodejs#13438
PR-URL: nodejs#13455
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>

src/inspector_agent.cc

@@ -371,7 +371,9 @@ void CallAndPauseOnStart(
   v8::MaybeLocal<v8::Value> retval =
       args[0].As<v8::Function>()->Call(env->context(), args[1],
                                        call_args.size(), call_args.data());
-  args.GetReturnValue().Set(retval.ToLocalChecked());
+  if (!retval.IsEmpty()) {
+    args.GetReturnValue().Set(retval.ToLocalChecked());
+  }
 }
 
 // Used in NodeInspectorClient::currentTimeMS() below.

test/inspector/test-inspector-exception.js

@@ -0,0 +1,64 @@
+'use strict';
+const common = require('../common');
+
+common.skipIfInspectorDisabled();
+
+const assert = require('assert');
+const helper = require('./inspector-helper.js');
+const path = require('path');
+
+const script = path.join(common.fixturesDir, 'throws_error.js');
+
+
+function setupExpectBreakOnLine(line, url, session) {
+  return function(message) {
+    if ('Debugger.paused' === message['method']) {
+      const callFrame = message['params']['callFrames'][0];
+      const location = callFrame['location'];
+      assert.strictEqual(url, session.scriptUrlForId(location['scriptId']));
+      assert.strictEqual(line, location['lineNumber']);
+      return true;
+    }
+  };
+}
+
+function testBreakpointOnStart(session) {
+  const commands = [
+    { 'method': 'Runtime.enable' },
+    { 'method': 'Debugger.enable' },
+    { 'method': 'Debugger.setPauseOnExceptions',
+      'params': {'state': 'none'} },
+    { 'method': 'Debugger.setAsyncCallStackDepth',
+      'params': {'maxDepth': 0} },
+    { 'method': 'Profiler.enable' },
+    { 'method': 'Profiler.setSamplingInterval',
+      'params': {'interval': 100} },
+    { 'method': 'Debugger.setBlackboxPatterns',
+      'params': {'patterns': []} },
+    { 'method': 'Runtime.runIfWaitingForDebugger' }
+  ];
+
+  session
+    .sendInspectorCommands(commands)
+    .expectMessages(setupExpectBreakOnLine(0, script, session));
+}
+
+function testWaitsForFrontendDisconnect(session, harness) {
+  console.log('[test]', 'Verify node waits for the frontend to disconnect');
+  session.sendInspectorCommands({ 'method': 'Debugger.resume'})
+    .expectStderrOutput('Waiting for the debugger to disconnect...')
+    .disconnect(true);
+}
+
+function runTests(harness) {
+  harness
+    .runFrontendSession([
+      testBreakpointOnStart,
+      testWaitsForFrontendDisconnect
+    ]).expectShutDown(1);
+}
+
+helper.startNodeForInspectorTest(runTests,
+                                 undefined,
+                                 undefined,
+                                 script);