Fix null pointer exception in TestNG when invalid options are used

Using invalid options through `cucumber.option` would cause the
creation of `testNGCucumberRunner` to fail with an exception. However
this exception does not terminate TestNGs execution. This caused
additional exceptions in the data provider and tear down methods. The
additional exceptions were mistaken for the root cause, creating some
confusion.

Author: mpkorstanje

CHANGELOG.md

@@ -7,6 +7,8 @@ Please see [CONTRIBUTING.md](https://github.com/cucumber/cucumber/blob/master/CO
 ### Deprecated
 ### Removed
 ### Fixed
+ * [TestNG] Fix null pointer exception when invalid options are used ([#1282](https://github.com/cucumber/cucumber-jvm/pull/1282), M.P. Korstanje)
+
 
 ## [2.1.0](https://github.com/cucumber/cucumber-jvm/compare/v2.0.1...v2.1.0)
 

testng/src/main/java/cucumber/api/testng/AbstractTestNGCucumberTests.java

@@ -29,11 +29,17 @@ public void runScenario(PickleEventWrapper pickleWrapper, CucumberFeatureWrapper
      */
     @DataProvider
     public Object[][] scenarios() {
+        if (testNGCucumberRunner == null) {
+            return new Object[0][0];
+        }
         return testNGCucumberRunner.provideScenarios();
     }
 
     @AfterClass(alwaysRun = true)
     public void tearDownClass() throws Exception {
+        if (testNGCucumberRunner == null) {
+            return;
+        }
         testNGCucumberRunner.finish();
     }
 }