HPCC-9634 Uninitialized members of ThorDataLinkMetaInfo

If a splitter has a null input (because pruned) the null input
implementation had uninitialized ThorDataLinkMetaInfo members.
I don't think any were of consequence, the critical members
totalRowsMin/Max were initialized.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>