Fix or indicate possible null pointer dereferencing detected by FindBugs

ludovicp

29.11.2008 aa4cddefb7237eea616db2b525539cc7c854d41a

 opends/src/server/org/opends/server/backends/jeb/VLVIndex.java

@@ -1885,6 +1885,7 @@
            resultCode = ResultCode.INVALID_ATTRIBUTE_SYNTAX;
          }
        }
        // BUG: attrType may be NULL
        sortKeys[i] = new SortKey(attrType, ascending[i]);
        orderingRules[i] = attrType.getOrderingMatchingRule();
      }