This fixes a bug in the fuzz target.
0echo 'OiAAAPr//wAAAAAAAAA=' | base64 --decode > /tmp/a
1UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" FUZZ=wallet_fees ./src/test/fuzz/fuzz /tmp/a
0wallet/fees.cpp:58:58: runtime error: implicit conversion from type 'unsigned int' of value 4294574080 (32-bit, unsigned) to type 'int' changed the value to -393216 (32-bit, signed)
1 [#0](/bitcoin-bitcoin/0/) 0x5625ef46a094 in wallet::GetMinimumFeeRate(wallet::CWallet const&, wallet::CCoinControl const&, FeeCalculation*) src/wallet/fees.cpp:58:58
2 [#1](/bitcoin-bitcoin/1/) 0x5625eedd467f in wallet::(anonymous namespace)::wallet_fees_fuzz_target(Span<unsigned char const>) src/wallet/test/fuzz/fees.cpp:64:11
3...
4
5SUMMARY: UndefinedBehaviorSanitizer: implicit-integer-sign-change wallet/fees.cpp:58:58 in