nat: Please coverity and initialize the saveptr to NULL

Coverity complains about the saveptr used in the strtok_r. This
is not a bug because we pass a string as part of the first call
to strtok_r but it is easier to just initialize it.

Addresses: Coverity CID 1042323
1 file changed
tree: ae56c4a1cf664ab02c039eb2b7fd031a2e800c07
  1. debian/
  2. hlrsync/
  3. linux-kernel/
  4. openbsc/
  5. wireshark/
  6. README