fixing plot_resolution_difference bug

[codecov[bot]]

Codecov Report

Patch coverage: 33.33% and project coverage change: +0.04 :tada:

Comparison is base (eafbe37) 63.15% compared to head (eaff1d8) 63.20%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #198 +/- ## ========================================== + Coverage 63.15% 63.20% +0.04% ========================================== Files 21 21 Lines 2717 2734 +17 ========================================== + Hits 1716 1728 +12 - Misses 1001 1006 +5 ``` | [Impacted Files](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory) | Coverage Δ | | |---|---|---| | [ctaplot/gammaboard/reader.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9nYW1tYWJvYXJkL3JlYWRlci5weQ==) | `0.00% <0.00%> (ø)` | | | [ctaplot/plots/style.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9wbG90cy9zdHlsZS5weQ==) | `100.00% <ø> (ø)` | | | [ctaplot/gammaboard/gammaboard.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9nYW1tYWJvYXJkL2dhbW1hYm9hcmQucHk=) | `11.81% <2.27%> (-0.10%)` | :arrow_down: | | [ctaplot/ana/ana.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9hbmEvYW5hLnB5) | `88.20% <86.66%> (-0.03%)` | :arrow_down: | | [ctaplot/\_\_init\_\_.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9fX2luaXRfXy5weQ==) | `100.00% <100.00%> (ø)` | | | [ctaplot/ana/tests/test\_ana.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9hbmEvdGVzdHMvdGVzdF9hbmEucHk=) | `100.00% <100.00%> (ø)` | | | [ctaplot/plots/plots.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9wbG90cy9wbG90cy5weQ==) | `78.49% <100.00%> (+0.02%)` | :arrow_up: | | [ctaplot/plots/tests/test\_plots.py](https://app.codecov.io/gh/cta-observatory/ctaplot/pull/198?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cta-observatory#diff-Y3RhcGxvdC9wbG90cy90ZXN0cy90ZXN0X3Bsb3RzLnB5) | `98.73% <100.00%> (+0.07%)` | :arrow_up: |

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