Fix the problem of iterating panic when the parameter is wrong

[wangchao0222]

Description

Fix the problem of iterating panic when the parameter is wrong

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

Brief of your solution

Please describe your solution to solve the issue or feature request.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

[codecov-commenter]

Codecov Report

Merging #346 (ad49b29) into master (88732a4) will decrease coverage by 0.03%. The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #346      +/-   ##
==========================================
- Coverage   45.43%   45.40%   -0.04%     
==========================================
  Files         142      142              
  Lines       12430    12434       +4     
==========================================
- Hits         5648     5646       -2     
- Misses       5626     5631       +5     
- Partials     1156     1157       +1     

Impacted Files	Coverage Δ
kernel/contract/sandbox/xmcache.go	46.61% <33.33%> (-1.45%)	:arrow_down:
bcs/consensus/tdpos/common.go	52.17% <0.00%> (-2.90%)	:arrow_down:
bcs/consensus/tdpos/tdpos.go	46.94% <0.00%> (-0.94%)	:arrow_down:
bcs/consensus/xpoa/xpoa.go	52.28% <0.00%> (+1.01%)	:arrow_up:

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