Infinite loop when applying element template

[Philipp Fromme]

Describe the Bug

After this commit and with element templates that contain properties with duplicate property IDs (here, here) and conditions depending on those applying an element template results in an infinite loop.

Steps to Reproduce

1. Check out infinite-loop branch
2. Run npm start
3. Test case fails

Expected Behavior

Test case passes. Deduplication IDs fixes it but also removing condition fixes it.

Environment

• Library version: 1.14.2

Additional Context

Initially reported via this thread

[Philipp Fromme]

Error only occurs when applying element template to existing element. Creating using bpmn-js-create-append-anything works.

[Philipp Fromme]

Added ready as we should fix this as soon as possible, either by validating IDs to be unique or by preventing the infinite loop.

[Nico Rehwaldt]

Fix via #82.