Guarantee instantiation result and thread_exception prior to access (#12013)

Author: MichelleArk

.changes/unreleased/Fixes-20250912-145113.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Guarantee instantiation result and thread_exception prior to access to avoid thread hangs
+time: 2025-09-12T14:51:13.355232-04:00
+custom:
+    Author: michelleark
+    Issue: "12013"

core/dbt/task/runnable.py

@@ -233,11 +233,14 @@ def call_runner(self, runner: BaseRunner) -> RunResult:
                     node_info=runner.node.node_info,
                 )
             )
+
+            result = None
+            thread_exception: Optional[Union[KeyboardInterrupt, SystemExit, Exception]] = None
             try:
                 result = runner.run_with_hooks(self.manifest)
             except (KeyboardInterrupt, SystemExit) as exe:
                 result = None
-                thread_exception: Union[KeyboardInterrupt, SystemExit, Exception] = exe
+                thread_exception = exe
                 raise
             except Exception as e:
                 result = None