EVM/Kernel: ignore transaction when caller is undefined

Context

A single transaction where the caller is undefined should not justify to exit the computation. As we do with invalid nonces, we ignore the transaction altogether.

Manually testing the MR

You can always manually test merge request by playing with the debugger:

$ make -f kernels.mk evm_kernel.wasm
$ rlwrap ./octez-smart-rollup-wasm-debugger evm_kernel.wasm --inputs tezt/tests/evm_kernel_inputs/inputs.json

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR