Only print the traceback if there was an exception.

ericsnowcurrently · ericsnowcurrently · commit cdb517d5ee1d · 2023-10-03T18:06:08.000-06:00
diff --git a/Modules/_xxsubinterpretersmodule.c b/Modules/_xxsubinterpretersmodule.c
@@ -450,11 +450,13 @@ _run_script(PyInterpreterState *interp, const char *codestr,
                 "RunFailedError: script raised an uncaught exception (%s)",
                 failure);
     }
-    // XXX Instead, store the rendered traceback on sharedexc,
-    // attach it to the exception when applied,
-    // and teach PyErr_Display() to print it.
-    PyErr_Display(NULL, excval, NULL);
-    Py_XDECREF(excval);
+    if (excval != NULL) {
+        // XXX Instead, store the rendered traceback on sharedexc,
+        // attach it to the exception when applied,
+        // and teach PyErr_Display() to print it.
+        PyErr_Display(NULL, excval, NULL);
+        Py_DECREF(excval);
+    }
     if (errcode != ERR_ALREADY_RUNNING) {
         _PyInterpreterState_SetNotRunningMain(interp);
     }
