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]>