[BUG] Refactor results iteration to ensure exception safety in search_duckduckgo

[coolbeevip]

Required prerequisites

• I have read the documentation https://camel-ai.github.io/camel/camel.html.
• I have searched the Issue Tracker and Discussions that this hasn't already been reported. (+1 or comment there if it has.)
• Consider asking first in a Discussion.

What version of camel are you using?

0.2.79a0

System information

import sys, camel
print(sys.version, sys.platform)
print(camel.version)
print(sys.version, sys.platform)
3.11.8 (main, Jan 14 2025, 13:47:38) [Clang 15.0.0 (clang-1500.3.9.4)] darwin
print(camel.version)
0.2.79a0

Problem description

The iteration over results in the search_duckduckgo method is currently outside the try block. This could lead to unhandled exceptions if results is not properly initialized due to an earlier RequestException.

Reproducible example code

1. Trigger a RequestException during the DuckDuckGo API call.
2. Observe that results may not be defined, leading to a runtime error during iteration.

Traceback

Expected behavior

No response

Additional context

No response

[fengju0213]

@coolbeevip thank you very much for the issue and pr!