If verification search fails low, return beta

[FauziAkram]

Same bench as master:
bench: 1441794

The original code checks if v >= beta after the verification search. However, if the verification search fails low (v < beta), it still returns nullValue.
With this change, if we can't beat beta, we return v, so we don't completly render the verification search useless.

Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 675040 W: 173934 L: 172755 D: 328351
Ptnml(0-2): 1813, 70154, 192463, 71221, 1869
https://tests.stockfishchess.org/tests/view/664739006dcff0d1d6b05cb9

*Let me know if an LTC test is needed.

bench: 1441794

[cj5716]

An LTC is needed, because it is functional at higher depths (keep in mind we only use verification search at depth 16 or higher, while bench is at depth 13)

[Disservin]

FauziAkram@eca018f#comments

@locutus2 pretty much already pointed out that an ltc is required and please drop the else there is no need for it.

I'll close this in the meantime feel free to open when ltc passes