eth_sendTransaction returns internal trace on missing param

[adisaran64]

Closes: #1275

Description

changes the eth_sendTransaction request to provide a properly formatted error (instead of an internal stack trace) when missing input params (the from field)

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
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• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #1284 (f611e7c) into main (f9c74e2) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #1284   +/-   ##
=======================================
  Coverage   52.13%   52.13%           
=======================================
  Files         105      105           
  Lines        9547     9547           
=======================================
  Hits         4977     4977           
  Misses       4302     4302           
  Partials      268      268           

Impacted Files	Coverage Δ
rpc/backend/sign_tx.go	0.00% <0.00%> (ø)

[facs95]

Thanks @adisaran64 ! This looks great. Please just remove those two lines and this should be ready to merge 👌

[fedekunze]

utACK. Can you add a bug-fix changelog entry?