Fix(UBSan): convertion NaN to unsigned int in Reservoir Sampler

[devcrafter]

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• Not for changelog (changelog entry is not required)

Fixes #42978

[devcrafter]

The fix is changing current behavior for empty column

CREATE TABLE default.quantile
(
    `a` UInt32
)
ENGINE = MergeTree
ORDER BY tuple()

Current:

SELECT median(a)
FROM quantile
    WITH TOTALS

Query id: 7d7341c8-e7c0-4365-b5b2-f3bafa100324

┌─median(a)─┐
│       nan │
└───────────┘

Totals:
┌─median(a)─┐
│       nan │
└───────────┘

New:

SELECT median(a)
FROM quantile
    WITH TOTALS

Query id: 7d7341c8-e7c0-4365-b5b2-f3bafa100324

┌─median(a)─┐
│       0   │
└───────────┘

Totals:
┌─median(a)─┐
│       0   │
└───────────┘

[devcrafter]

fixed in #44067