Fix DatePicker year picker crash in range mode

[Coderxrohan]

Issue:
In DatePicker range mode, the selected value is an array ([startDate, endDate] or [Date, null]), but year-selection logic treated it as a single Date. This caused getFullYear() to be called on non-Date values, resulting in a runtime crash when opening the year picker.

Fix:
Updated the year-selection logic to correctly handle array-based values by normalizing the selection before accessing year data. Array (range/multiple) cases are now handled before single-date logic, ensuring getFullYear() is only called on valid Date instances.

Fixes #8468
([v11] Datepicker: Error when trying to select the year after selecting a date in range mode.)

[Coderxrohan]

@ThiagoBarbosaDev thanks for the clear bug report and repro steps — they helped a lot. I’ve submitted a fix handling range values correctly in the year picker. Please feel free to verify and let me know if any adjustments are needed.

[x10vaishnavi]

Looked through the changes — handling the array cases before the single date logic is the right call.
This will really avoids the crash and keeps the year picking logic clean..

[melloware]

Assigned to PrimeTek to review

[Coderxrohan]

Assigned to PrimeTek to review

Thanks for the update. Happy to wait for the PrimeTek review.
Let me know if any changes or follow-ups are needed from my side.

[melloware]

@Coderxrohan much appreciated all your work and your thorough explanations! They really help maintainers.