Fix invalid empty-state range in getShowingInfo()

[RA9]

Description

When _data is empty, getShowingInfo() computes startIndex = 1 and endIndex = min(1 + perPage - 1, 0) = 0, producing the nonsensical string "Showing 1 to 0 of 0 items".

Steps to reproduce

const table = new EzyTables({ clientEnabled: true, data: [], ... });
console.log(table.getShowingInfo()); // "Showing 1 to 0 of 0 items ."

Expected behavior

Return "No items to show" (or equivalent) when totalItems === 0.