fix(validator): reject numeric character references with no digits (&#; and &#x;)

[sravan27]

Bug

XMLValidator.validate reports malformed numeric character references as valid:

const { XMLValidator } = require("fast-xml-parser");
XMLValidator.validate("<r>&#x;</r>"); // true  (should be invalid)
XMLValidator.validate("<r>&#;</r>");  // true  (should be invalid)
XMLValidator.validate("<r>&#xG;</r>");// {err:...} invalid  (control — bad hex IS rejected)

Per the XML 1.0 CharRef production, a numeric reference must contain at least one digit (&#[0-9]+; or &#x[0-9a-fA-F]+;). &#; and &#x; have none.

Cause

src/validator.js, validateNumberAmpersand: the scan loop checks for ; before requiring any digit, so a ; immediately following &# or &#x returns a success index with zero digits consumed.

for (; i < xmlData.length; i++) {
  if (xmlData[i] === 

[amitguptagwl]

@sarahdayan , please try with 'fast-xml-validator' and let me know.