FIX buffer overflow for malformed QUIC initial packet

[codecov-commenter]

Codecov Report

Patch coverage: 39.82% and project coverage change: -0.06% :warning:

Comparison is base (5dc1509) 41.50% compared to head (eb33f25) 41.45%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #181 +/- ## ========================================== - Coverage 41.50% 41.45% -0.06% ========================================== Files 92 92 Lines 8584 8622 +38 Branches 1295 1298 +3 ========================================== + Hits 3563 3574 +11 - Misses 4255 4280 +25 - Partials 766 768 +2 ``` | [Flag](https://app.codecov.io/gh/CESNET/ipfixprobe/pull/181/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CESNET) | Coverage Δ | | |---|---|---| | [tests](https://app.codecov.io/gh/CESNET/ipfixprobe/pull/181/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CESNET) | `41.45% <39.82%> (-0.06%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CESNET#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files Changed](https://app.codecov.io/gh/CESNET/ipfixprobe/pull/181?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CESNET) | Coverage Δ | | |---|---|---| | [process/quic\_parser.cpp](https://app.codecov.io/gh/CESNET/ipfixprobe/pull/181?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CESNET#diff-cHJvY2Vzcy9xdWljX3BhcnNlci5jcHA=) | `41.25% <39.82%> (-1.11%)` | :arrow_down: |

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