fix: add system transaction check in collect_system_reward (#63)

[pythonberg1997]

Description

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Example

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Changes

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[github-actions]

Valgrind Results:

==6618== Cachegrind, a cache and branch-prediction profiler
==6618== Copyright (C) 2002-2017, and GNU GPL'd, by Nicholas Nethercote et al.
==6618== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==6618== Command: target/release/snailtracer
==6618== 
--6618-- warning: L3 cache found, using its data for the LL simulation.
Running snailtracer example!
elapsed: 1.798489226s
==6618== 
==6618== I   refs:      427,738,241
==6618== I1  misses:          3,171
==6618== LLi misses:          2,832
==6618== I1  miss rate:        0.00%
==6618== LLi miss rate:        0.00%
==6618== 
==6618== D   refs:      204,083,476  (132,274,350 rd   + 71,809,126 wr)
==6618== D1  misses:        340,553  (    200,601 rd   +    139,952 wr)
==6618== LLd misses:        137,639  (      4,347 rd   +    133,292 wr)
==6618== D1  miss rate:         0.2% (        0.2%     +        0.2%  )
==6618== LLd miss rate:         0.1% (        0.0%     +        0.2%  )
==6618== 
==6618== LL refs:           343,724  (    203,772 rd   +    139,952 wr)
==6618== LL misses:         140,471  (      7,179 rd   +    133,292 wr)
==6618== LL miss rate:          0.0% (        0.0%     +        0.2%  )