tdf#89214 SwDoc::GetUniqueNumRuleName: always return pChkStr if it's unused

Regression from commit bb00a00979 (do not
bother with nice unique names during mailmerge, 2014-11-08),
SwAttrSet::CopyToModify() expects that in case SwDoc::FindNumRulePtr()
returns 0 for a name, then the call to SwDoc::MakeNumRule() will use the
not found name (as SwDoc::GetUniqueNumRuleName() will return the just
checked name).

As a result, simply always returning a random unique name during mail
merge is a problem. Only return a cheap random unique name if no hint is
given.

Change-Id: I49d65009ced97d00aa2e8db35a529f2f30ac9ae5

sw/qa/extras/mailmerge/mailmerge.cxx

@@ -394,5 +394,17 @@ DECLARE_SHELL_MAILMERGE_TEST(testPageBoundaries2Pages, "simple-mail-merge-2pages
     }
 }
 
+DECLARE_SHELL_MAILMERGE_TEST(testTdf89214, "tdf89214.odt", "10-testing-addresses.ods", "testing-addresses")
+{
+    executeMailMerge();
+
+    uno::Reference<text::XTextDocument> xTextDocument(mxMMComponent, uno::UNO_QUERY);
+    uno::Reference<text::XTextRange> xParagraph(getParagraphOrTable(3, xTextDocument->getText()), uno::UNO_QUERY);
+    // Make sure that we assert the right paragraph.
+    CPPUNIT_ASSERT_EQUAL(OUString("a"), xParagraph->getString());
+    // This paragraph had a bullet numbering, make sure that the list id is not empty.
+    CPPUNIT_ASSERT(!getProperty<OUString>(xParagraph, "ListId").isEmpty());
+}
+
 CPPUNIT_PLUGIN_IMPLEMENT();
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

sw/source/core/doc/docnum.cxx

@@ -2178,13 +2178,13 @@ sal_uInt16 SwDoc::MakeNumRule( const OUString &rName,
 
 OUString SwDoc::GetUniqueNumRuleName( const OUString* pChkStr, bool bAutoNum ) const
 {
-    if( IsInMailMerge())
+    // If we got pChkStr, then the caller expects that in case it's not yet
+    // used, it'll be returned.
+    if( IsInMailMerge() && !pChkStr )
     {
         OUString newName = "MailMergeNumRule"
             + OStringToOUString( DateTimeToOString( DateTime( DateTime::SYSTEM )), RTL_TEXTENCODING_ASCII_US )
             + OUString::number( mpNumRuleTbl->size() + 1 );
-        if( pChkStr )
-            newName += *pChkStr;
         return newName;
     }