Add additional error handling in determine_chrome_version.

BUG=chromium:1017583
TEST=manual, run_tests

Change-Id: I9010fdc4ba42465902f453722440f78879bcbb74
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1888631
Tested-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
Reviewed-by: David Burger <dburger@chromium.org>
diff --git a/api/controller/packages_unittest.py b/api/controller/packages_unittest.py
index 85fb125..b421f8f 100644
--- a/api/controller/packages_unittest.py
+++ b/api/controller/packages_unittest.py
@@ -305,6 +305,15 @@
                                          self.api_config)
     self.assertEqual(self.response.version, chrome_version)
 
+  def testGetChromeVersionHandleNone(self):
+    """Verify basic return values."""
+    self.PatchObject(packages_service, 'determine_chrome_version',
+                     return_value=None)
+    request = self._GetRequest(board='betty')
+    packages_controller.GetChromeVersion(request, self.response,
+                                         self.api_config)
+    self.assertFalse(self.response.version)
+
 
 class GetTargetVersionsTest(cros_test_lib.MockTestCase, ApiConfigMixin):
   """GetTargetVersions tests."""