fix: handle XmlValueNotSupportedException for decimal twips in XWPFUt…

[shakeel-mushtaq]

…ils.floatValue()

OOXML documents generated by certain tools (e.g. LibreOffice, some Word automation libraries) may store table grid column widths as non-integer decimal values (e.g. w:w="3457.7537212449256"). The XML Schema type STTwipsMeasure / STSignedTwipsMeasure / STMeasurementOrPercent are defined as xs:union types, so XMLBeans represents such values as XmlUnionImpl. Calling getFloatValue() on that union throws:

XmlValueNotSupportedException: Could not get a Java numeric type
from a Schema string type

This cascades up through XWPFTableUtil.getGridColList() and crashes the entire XHTML converter with an XWPFConverterException, making thumbnail and preview generation impossible for affected documents.

Fix:

• Wrap getFloatValue() in the three floatValue() overloads with a try/catch that falls back to parseSafeFloat().
• parseSafeFloat() retrieves the raw string value and handles:
  • Decimal twips strings (e.g. "3457.75") → parsed via Float.parseFloat()
  • Percentage strings (e.g. "50%") → divided by 100
  • The literal "auto" → 0.0f
  • Any remaining unparseable value → 0.0f (safe fallback)
• Added null-guards on all three overloads.

Reproducer: a .docx whose word/document.xml contains
<w:gridCol w:w="3457.7537212449256"/>
will now convert successfully instead of throwing.