spec.source_code_spec.inline_source.source_archive` cannot be empty

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**Describe the bug**
when deploying adk to adk deploy agent_engine using "adk deploy agent_engine" and trying to Enable instrumentation of OpenTelemetry traces and logs I get the error _spec.source_code_spec.inline_source.source_archive` cannot be empty_

**To Reproduce**
Please share a minimal code and data to reproduce your problem.
Steps to reproduce the behavior:
1. adk deploy agent_engine myagent --trace_to_cloud
2. try to Enable instrumentation of OpenTelemetry traces and logs using the Service configuration panel in the GCP console
3. Press update

**Expected behavior**
Telemetry collection enabled

**Screenshots**

**Desktop (please complete the following information):**
- OS: macOS
- Python version(python -V): 3.13.2
- ADK version(pip show google-adk): 1.18.0

**Model Information:**
- Are you using LiteLLM: No
- Which model is being used: gemini-2.5-fals

**Additional context**
Add any other context about the problem here.