fix(asm): do not imply the callback is registered (#8074)

Following #8057 allowing less
import if appsec is not loaded, wsgi_environ may not be registered. But
the wrapper was making the assumption it was always registered.
This PR fixes that.

No changelog needed as it's fixing an unreleased bug.

Note: Bug was detected on python3.12 weblog on system-tests

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)
- [x] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [x] This PR doesn't touch any of that.

Author: christophe-papazian

ddtrace/contrib/django/patch.py

@@ -27,6 +27,7 @@
 from ddtrace.internal.constants import COMPONENT
 from ddtrace.internal.constants import HTTP_REQUEST_BLOCKED
 from ddtrace.internal.constants import STATUS_403_TYPE_AUTO
+from ddtrace.internal.core.event_hub import ResultType
 from ddtrace.internal.logger import get_logger
 from ddtrace.internal.schema import schematize_service_name
 from ddtrace.internal.schema import schematize_url_operation
@@ -822,7 +823,16 @@ def _(m):
 
 
 def wrap_wsgi_environ(wrapped, _instance, args, kwargs):
-    return core.dispatch_with_results("django.wsgi_environ", (wrapped, _instance, args, kwargs)).wrapped_result.value
+    result = core.dispatch_with_results("django.wsgi_environ", (wrapped, _instance, args, kwargs)).wrapped_result
+    # if the callback is registered and runs, return the result
+    if result:
+        return result.value
+    # if the callback is not registered, return the original result
+    elif result.response_type == ResultType.RESULT_UNDEFINED:
+        return wrapped(*args, **kwargs)
+    # if an exception occurs, raise it. It should never happen.
+    elif result.exception:
+        raise result.exception
 
 
 def patch():