fixed a minor typo in a string (as a result of review, see trac #116)

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@1906 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/dns/rdata/generic/nsec_47.cc

@@ -112,7 +112,7 @@ NSEC::NSEC(InputBuffer& buffer, size_t rdata_len) {
     for (int i = 0; i < rdata_len; i += len) {
         if (i + 2 > rdata_len) {
             isc_throw(DNSMessageFORMERR, "NSEC RDATA from wire: "
-                      "incomplete bit map filed");
+                      "incomplete bit map field");
         }
         block = typebits[i];
         len = typebits[i + 1];