fix: remove ability to send zero amount fungible token messages

[QEDK]

Pull Request type

Please add the labels corresponding to the type of changes your PR introduces:

• [ ] Feature
• [X] Bugfix
• [ ] Refactor
• [ ] Format
• [ ] Documentation
• [ ] Testing
• [ ] Other:

Description

• This PR removes the ability for users to send send message fungible token extrinsics with zero amounts

Related Issues

Testing Performed

• Added a negative test-case that checks for the relevant error

Checklist

• [X] I have performed a self-review of my own code.
• [X] The tests pass successfully with cargo test.
• [X] The code was formatted with cargo fmt.
• [X] The code compiles with no new warnings with cargo build --release and cargo build --release --features runtime-benchmarks.
• [X] The code has no new warnings when using cargo clippy.
• [X] If this change affects documented features or needs new documentation, I have created a PR with a documentation update.