chore(iast): django Invalid or empty source_value

[avara1986]

Fix telemetry log error: "ValueError: [IAST] Invalid or empty source_value."

No release note needed, as this error occurs after this PR #10740 that has not been released yet

Task APPSEC-55017

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

.gitlab/tests/appsec.yml                                                @DataDog/asm-python
ddtrace/appsec/_handlers.py                                             @DataDog/asm-python
ddtrace/appsec/_iast/_metrics.py                                        @DataDog/asm-python
ddtrace/appsec/_iast/_taint_tracking/__init__.py                        @DataDog/asm-python
tests/appsec/iast/conftest.py                                           @DataDog/asm-python
tests/appsec/iast/test_processor.py                                     @DataDog/asm-python
tests/appsec/iast/test_telemetry.py                                     @DataDog/asm-python
tests/contrib/django/django_app/appsec_urls.py                          @DataDog/asm-python
tests/contrib/django/test_django_appsec_iast.py                         @DataDog/asm-python
tests/contrib/fastapi/test_fastapi_appsec_iast.py                       @DataDog/asm-python

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-09-26 14:02:53

Comparing candidate commit ae44cc3 in PR branch avara1986/fix_empty_source_value_2 with baseline commit 0e1f4eb in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 359 metrics, 53 unstable metrics.

[github-actions]

The backport to 2.13 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.13 2.13
# Navigate to the new working tree
cd .worktrees/backport-2.13
# Create a new branch
git switch --create backport-10816-to-2.13
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 26d9c60679fecc6cace5e405b361e7aed8429757
# Push it to GitHub
git push --set-upstream origin backport-10816-to-2.13
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.13

Then, create a pull request where the base branch is 2.13 and the compare/head branch is backport-10816-to-2.13.