Add nil checking

[goccy]

SSIA

[github-actions]

Code Metrics Report

	main (afb1d4a)	#220 (e0f6daa)	+/-
Coverage	65.1%	65.1%	-0.0%
Code to Test Ratio	1:0.3	1:0.3	-0.0
Test Execution Time	7m19s	6m47s	-32s

Details

  |                     | main (afb1d4a) | #220 (e0f6daa) |  +/-  |
  |---------------------|----------------|----------------|-------|
- | Coverage            |          65.1% |          65.1% | -0.0% |
  |   Files             |             69 |             69 |     0 |
  |   Lines             |          11746 |          11749 |    +3 |
+ |   Covered           |           7650 |           7651 |    +1 |
- | Code to Test Ratio  |          1:0.3 |          1:0.3 |  -0.0 |
  |   Code              |          37045 |          37054 |    +9 |
  |   Test              |          12653 |          12653 |     0 |
+ | Test Execution Time |          7m19s |          6m47s |  -32s |

Code coverage of files in pull request scope (81.7% → 81.7%)

Files	Coverage	+/-
resolver/resolver.go	81.7%	-0.1%

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Reported by octocov