Avoid assert failure when NULL EC is expected

After 5680c38c75aeb5cbd219aafa8eb48c315f287d97, postponed job APIs now
expect to be called on native threads not managed by Ruby and handles
getting a NULL execution context. However, in debug builds the change
runs into an assertion failure with GET_EC() which asserts that EC is
non-NULL. Avoid the assertion failure by passing `false` for `expect_ec`
instead as the intention is to handle when there is no EC.

Add a test from John Crepezzi and John Hawthorn to exercise this
situation.

See GH-4108
See GH-5094

[Bug #17573]

Co-authored-by: John Hawthorn <[email protected]>
Co-authored-by: John Crepezzi <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/vm_trace.c b/vm_trace.c
index 3bc55f2c3a..66ea7b24b7 100644
--- a/vm_trace.c
+++ b/vm_trace.c
@@ -1585,7 +1585,7 @@ postponed_job_register(rb_execution_context_t *ec, rb_vm_t *vm,
 static rb_execution_context_t *
 get_valid_ec(rb_vm_t *vm)
 {
-    rb_execution_context_t *ec = GET_EC();
+    rb_execution_context_t *ec = rb_current_execution_context(false);
     if (ec == NULL) ec = rb_vm_main_ractor_ec(vm);
     return ec;
 }