fix: Ensure safe assignment to tool_blocks_map in agent_message handling

[ogabrielluiz]

This PR adds a safety check to ensure that the assignment to tool_blocks_map is only performed when agent_message.content_blocks and its contents are available. This prevents potential errors when accessing these properties.

[Cristhianzl]

lgtm

[codspeed-hq]

CodSpeed Performance Report

Merging #5239 will improve performances by 85.76%

_{Comparing guard-clause-contents (81e16f2) with main (c6b1eab)}

Summary

⚡ 5 improvements
✅ 10 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	guard-clause-contents	Change
⚡	test_get_and_cache_all_types_dict	1,097 µs	948.5 µs	+15.66%
⚡	test_load_flows	2 ms	1.1 ms	+85.76%
⚡	test_setup_llm_caching	2 ms	1.2 ms	+70.48%
⚡	test_successful_run_with_input_type_any	254.5 ms	209.4 ms	+21.5%
⚡	test_successful_run_with_output_type_any	242.2 ms	200.6 ms	+20.71%