fix: fix uncaught TypeError if error occurs on next tick, closes moch…

…ajs#2315 (mochajs#2439)

lib/runner.js

@@ -420,6 +420,9 @@ Runner.prototype.runTest = function(fn) {
   var self = this;
   var test = this.test;
 
+  if (!test) {
+    return;
+  }
   if (this.asyncOnly) {
     test.asyncOnly = true;
   }

test/integration/fixtures/regression/issue-2315.js

@@ -0,0 +1,7 @@
+describe('issue-2315: cannot read property currentRetry of undefined', function () {
+  before(function () {
+    require('http').createServer().listen(1);
+  });
+
+  it('something', function () {});
+});

test/integration/regression.spec.js

@@ -1,4 +1,4 @@
-var assert  = require('assert');
+var assert  = require('assert');
 var fs      = require('fs');
 var path    = require('path');
 var run     = require('./helpers').runMocha;
@@ -62,6 +62,17 @@ describe('regressions', function() {
     });
   });
 
+  it('issue-2315: cannot read property currentRetry of undefined', function (done) {
+    runJSON('regression/issue-2315.js', [], function(err, res) {
+      assert(!err);
+      assert.equal(res.stats.pending, 0);
+      assert.equal(res.stats.passes, 0);
+      assert.equal(res.stats.failures, 1);
+      assert.equal(res.code, 1);
+      done();
+    });
+  });
+
   it('issue-2406: should run nested describe.only suites', function(done) {
     this.timeout(2000);
     runJSON('regression/issue-2406.fixture.js', [], function(err, res) {