hwpf: ignore null-reference to parent stylesheet (bug#50688)

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1065535 13f79535-47bb-0310-9956-ffa450edef68

src/scratchpad/src/org/apache/poi/hwpf/model/StyleSheet.java

@@ -238,6 +238,10 @@ public final class StyleSheet implements HDFType {
 
           }
 
+          if (parentPAP == null) {
+              parentPAP = new ParagraphProperties();
+          }
+
           pap = ParagraphSprmUncompressor.uncompressPAP(parentPAP, papx, 2);
           sd.setPAP(pap);
       }

src/scratchpad/testcases/org/apache/poi/hwpf/extractor/TestWordExtractorBugs.java

@@ -38,4 +38,13 @@ public final class TestWordExtractorBugs extends TestCase {
 		extractor.getParagraphText();
 		extractor.getTextFromPieces();
 	}
+
+    public void testBug50688() throws Exception {
+        WordExtractor extractor =
+            new WordExtractor(POIDataSamples.getDocumentInstance().openResourceAsStream("parentinvguid.doc"));
+
+        // Check it gives text without error
+        extractor.getText();
+    }
+    
 }