fix: ensure option is used to remove warning

[glihm]

When testing with the new 0.9.0 version, we had some warning when compiling a project:

warning: Unhandled `#[must_use]` type `core::option::Option::<@core::felt252>`
 --> /home/.cache/scarb/registry/git/checkouts/cairo-contracts-9cboa8jg3jldq/861fc41/src/tests/utils.cairo:26:5
    keys.pop_front();
    ^**************^

warning: Unhandled `#[must_use]` type `core::option::Option::<(core::array::Span::<core::felt252>, core::array::Span::<core::felt252>)>`
 --> /home/.cache/scarb/registry/git/checkouts/cairo-contracts-9cboa8jg3jldq/861fc41/src/tests/utils.cairo:51:5
    testing::pop_log_raw(address);
    ^***************************^

warning: Unhandled `#[must_use]` type `core::option::Option::<@core::felt252>`
 --> /home/.cache/scarb/registry/git/checkouts/cairo-contracts-9cboa8jg3jldq/861fc41/src/tests/utils.cairo:26:5
    keys.pop_front();
    ^**************^

warning: Unhandled `#[must_use]` type `core::option::Option::<(core::array::Span::<core::felt252>, core::array::Span::<core::felt252>)>`
 --> /home/.cache/scarb/registry/git/checkouts/cairo-contracts-9cboa8jg3jldq/861fc41/src/tests/utils.cairo:51:5
    testing::pop_log_raw(address);
    ^***************************^

Checking on main, this issue is still present.
This PR aims at using the Option to avoid warnings.

PR Checklist

It's a very small fix for warnings, the test suite passes but I've not deployed a contract on public network as the issue is related to testing only. Not sure if the CHANGELOG applies in this occasion, but will be happy to complete any missing item. 👍

• Tests
• Documentation
• Added entry to CHANGELOG.md
• Tried the feature on a public network

[ericnordelo]

Thanks for reporting and taking the time!

[glihm]

@ericnordelo sorry then for the lack of pertinence here, appreciate your feedback and context. 👍

[ericnordelo]

LGTM!

[andrew-fleming]

LGTM! Thanks, @glihm!