vm: increase code coverage of source_text_module.js
1 more line of code coverage: https://coverage.nodejs.org/coverage-1a4f27ae21698d0c/lib/internal/vm/source_text_module.js.html#L161
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines