Fixes following pandas 2

[dnerini]

Minor adjustments following the release of pandas 2:

• in tdating.py use pd.concat instead of pd.DataFrame().append which was effectively removed (ref).
• in salscores.py: Division by zero returns -inf, nan, or inf depending on the numerator, instead of raising (but I wasn't able to understand exactly the root cause of this breaking change...)

Additionally,

• Fix scipy.ndimage's DeprecationWarnings
• Fix pandas' SettingWithCopyWarnings

[codecov[bot]]

Codecov Report

Patch coverage: 93.47% and project coverage change: -0.01 :warning:

Comparison is base (1c90e44) 83.34% compared to head (c527501) 83.34%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #327 +/- ## ========================================== - Coverage 83.34% 83.34% -0.01% ========================================== Files 161 161 Lines 12359 12355 -4 ========================================== - Hits 10301 10297 -4 Misses 2058 2058 ``` | Flag | Coverage Δ | | |---|---|---| | unit_tests | `83.34% <93.47%> (-0.01%)` | :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=pySTEPS#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS) | Coverage Δ | | |---|---|---| | [pysteps/motion/constant.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9tb3Rpb24vY29uc3RhbnQucHk=) | `33.33% <50.00%> (ø)` | | | [pysteps/extrapolation/semilagrangian.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9leHRyYXBvbGF0aW9uL3NlbWlsYWdyYW5naWFuLnB5) | `70.10% <66.66%> (ø)` | | | [pysteps/blending/steps.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9ibGVuZGluZy9zdGVwcy5weQ==) | `83.89% <100.00%> (ø)` | | | [pysteps/feature/tstorm.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9mZWF0dXJlL3RzdG9ybS5weQ==) | `94.16% <100.00%> (-0.24%)` | :arrow_down: | | [pysteps/motion/vet.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9tb3Rpb24vdmV0LnB5) | `87.33% <100.00%> (ø)` | | | [pysteps/nowcasts/sseps.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9ub3djYXN0cy9zc2Vwcy5weQ==) | `87.19% <100.00%> (ø)` | | | [pysteps/nowcasts/steps.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9ub3djYXN0cy9zdGVwcy5weQ==) | `81.45% <100.00%> (ø)` | | | [pysteps/nowcasts/utils.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy9ub3djYXN0cy91dGlscy5weQ==) | `97.57% <100.00%> (ø)` | | | [pysteps/tracking/tdating.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy90cmFja2luZy90ZGF0aW5nLnB5) | `91.53% <100.00%> (+0.06%)` | :arrow_up: | | [pysteps/verification/salscores.py](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS#diff-cHlzdGVwcy92ZXJpZmljYXRpb24vc2Fsc2NvcmVzLnB5) | `90.42% <100.00%> (ø)` | | | ... and [1 more](https://codecov.io/gh/pySTEPS/pysteps/pull/327?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS) | | ... and [28 files with indirect coverage changes](https://codecov.io/gh/pySTEPS/pysteps/pull/327/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS) Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS)

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