shopify-scripts: Segfault in mruby, mruby_engine and the parent MRI Ruby due to null pointer dereference

Introduction ============ Certain valid Ruby programs are able to cause a segmentation fault in mruby through a null pointer derefence, which in turn leads to a crash in mrubyengine and the parent MRI Ruby process. Proof of concept ================ crash.rb: --------- def method yield end method&...