Handle empty EUI64 manufacturing tokens

[puddly]

https://github.com/home-assistant/core/issues/95592

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (a7173ca) 99.77% compared to head (bce6a1d) 99.77%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #570 +/- ## ======================================= Coverage 99.77% 99.77% ======================================= Files 67 67 Lines 4831 4836 +5 ======================================= + Hits 4820 4825 +5 Misses 11 11 ``` | [Impacted Files](https://app.codecov.io/gh/zigpy/bellows/pull/570?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy) | Coverage Δ | | |---|---|---| | [bellows/ezsp/\_\_init\_\_.py](https://app.codecov.io/gh/zigpy/bellows/pull/570?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy#diff-YmVsbG93cy9lenNwL19faW5pdF9fLnB5) | `99.30% <100.00%> (+0.01%)` | :arrow_up: |

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