trigger_* methods should be protected against missing an UI context

[mwestphal]

Describe the bug
many trigger_* methods segfault if render() has not been called beforehand, lets fix that

To Reproduce
Steps to reproduce the behavior:

1. In library/testing/TestSDKTriggerInteractions.cxx comment out engine.getWindow().render();
2. build
3. run ctest -R TestSDKTriggerInteractions
4. Segfault

Expected behavior
No segfault but an error

[Samarthi]

Hi @mwestphal , I'd like to work on this issue.