Fix paymaster-less v0.7 AA encoding

[0xFirekeeper]

Fixes TOOL-3952

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PR-Codex overview

This PR focuses on improving the handling of the Paymaster in the PackedUserOperation. It introduces conditional logic to handle cases where the Paymaster is null or set to a specific address, ensuring the PaymasterAndData is properly initialized.

Detailed summary

• Introduced a conditional check for userOp.Paymaster.
• If Paymaster is null or a specific address, PaymasterAndData is set to an empty array.
• Otherwise, the Paymaster and related data are processed and copied to paymasterAndDataBuffer.
• PackedUserOperation is created based on the conditional logic.

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[linear]

TOOL-3952 Fix paymaster-less v0.7 AA encoding issue

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 60.52632% with 15 lines in your changes missing coverage. Please review.

Project coverage is 61.98%. Comparing base (59f7ed8) to head (efdb859).

Files with missing lines	Patch %	Lines
...irdweb/Thirdweb.Wallets/SmartWallet/SmartWallet.cs	60.52%	14 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #143      +/-   ##
==========================================
- Coverage   62.17%   61.98%   -0.19%     
==========================================
  Files          41       41              
  Lines        6157     6174      +17     
  Branches      795      796       +1     
==========================================
- Hits         3828     3827       -1     
- Misses       2152     2169      +17     
- Partials      177      178       +1     

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