fix for issue 690

git-svn-id: https://tesseract-ocr.googlecode.com/svn/trunk@736 d0cd1f9f-072b-0410-8dd7-cf729c803f20

ccmain/resultiterator.cpp

@@ -585,6 +585,7 @@ char* ResultIterator::GetUTF8Text(PageIteratorLevel level) const {
       }
       break;
   }
+  if (text.string() == NULL) return NULL;
   int length = text.length() + 1;
   char* result = new char[length];
   strncpy(result, text.string(), length);