(related: fdo#78502) writerfilter: RTF import: fix invalid string copy

... in leveltext destination.

Change-Id: I74de6d14170130bf33923854a0c9851dc7cc390f

writerfilter/source/rtftok/rtfdocumentimpl.cxx

@@ -4827,7 +4827,7 @@ int RTFDocumentImpl::popState()
         // The first character is the length of the string (the rest should be ignored).
         sal_Int32 nLength(aStr.toChar());
         OUString aValue;
-        if (nLength <= aStr.getLength())
+        if (nLength < aStr.getLength())
             aValue = aStr.copy(1, nLength);
         else
             aValue = aStr;