Safeguard dpss settings

[tensionhead]

Changes Summary

• the taper bandwidths could be 0.99999999.. which then gets cast to 0

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (4ca4ea2) 69.29% compared to head (a2ea42f) 69.29%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #562 +/- ## ======================================= Coverage 69.29% 69.29% ======================================= Files 87 87 Lines 10122 10123 +1 Branches 2125 2125 ======================================= + Hits 7014 7015 +1 Misses 2534 2534 Partials 574 574 ``` | [Files Changed](https://app.codecov.io/gh/esi-neuroscience/syncopy/pull/562?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=esi-neuroscience) | Coverage Δ | | |---|---|---| | [syncopy/specest/mtmfft.py](https://app.codecov.io/gh/esi-neuroscience/syncopy/pull/562?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=esi-neuroscience#diff-c3luY29weS9zcGVjZXN0L210bWZmdC5weQ==) | `100.00% <100.00%> (ø)` | |

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