Adding Null Pointer check

[prafulVaishnav]

No description provided.

[prafulVaishnav]

Function ctPageBreak.getVal() (https://github.com/apache/poi/blob/trunk/src/ooxml/java/org/apache/poi/xwpf/usermodel/XWPFParagraph.java#L824) returns null in some cases. So adding Null Pointer check.

To reproduce the issue, use the attached docx file (sample.docx) and run below code:

InputStream is = new FileInputStream("<attachedFilePath>");
		XWPFDocument docx = new XWPFDocument(is);
		Iterator<XWPFParagraph> paraIter = docx.getParagraphsIterator();
		while (paraIter.hasNext()) {
			XWPFParagraph para = paraIter.next();
			if (para.isEmpty()) {
				//do Something
			}
		}

Function para.isEmpty() will throw NPE.

@tballison @poi-benchmark Please review and merge.

[onealj]

Possible side-note, but shouldn't we be checking that the value isn't any of the true-like string values that OOXML STOnOff allows: "true", "1", or "on"?

[onealj]

Thanks for the pull request and unit test. I didn't include your unit test or sample document in our unit test suite because it's a simple NPE. There weren't any other issues uncovered by the integration testing (org.apache.poi.stress.XWPFFileHandler(document/github53.docx)) with this file.

I also took the opportunity to change isPageBreak to work for all of the boolean-like value: "true", "1", "on", "false", "0", "off".

These changes will be included in POI 3.17 beta 1.

r1795254 https://svn.apache.org/viewvc?view=revision&revision=1795254