fix: avoid crashing when asm env doesnt exist during finalise() [backport 1.18] (#6848)

Backport d534fd5 from #6669 to 1.18.

This fix addresses the crash described in
#6659 by defensively
handling `None` values for the `asm_env` object during `_DataHandler`
shutdown. The root cause of this issue is unknown.

There are no tests added here because we don't have a replication case.

## 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)

Co-authored-by: Emmett Butler <[email protected]>
Co-authored-by: Munir Abdinur <[email protected]>

Author: 3 people

ddtrace/appsec/_asm_request_context.py

@@ -130,11 +130,13 @@ def __init__(self):
     def finalise(self):
         if self.active:
             env = self.execution_context.get_item("asm_env")
-            # assert _CONTEXT_ID.get() == self._id
-            callbacks = GLOBAL_CALLBACKS.get(_CONTEXT_CALL, []) + env.callbacks.get(_CONTEXT_CALL)
-            if callbacks is not None:
-                for function in callbacks:
-                    function(env)
+            callbacks = GLOBAL_CALLBACKS.get(_CONTEXT_CALL, [])
+            if env is not None and env.callbacks is not None and env.callbacks.get(_CONTEXT_CALL):
+                callbacks += env.callbacks.get(_CONTEXT_CALL)
+            if callbacks:
+                if env is not None:
+                    for function in callbacks:
+                        function(env)
                 self.execution_context.end()
             self.active = False
 

releasenotes/notes/missing-asm-env-9a2eaa4936c35e0d.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    appsec: This fix resolves an issue in which the library attempted to finalize twice a context object used
+    by the Application Security Management product.