Fix memory leak in Optimized CPU degridder kernel
A minor memory leak in the degridder kernel caused lots of memory to be leaked for long runs with large datasets, where this leak is triggered many times.
Before:
==4723== LEAK SUMMARY:
==4723== definitely lost: 10,452,992 bytes in 2,552 blocks
==4723== indirectly lost: 0 bytes in 0 blocks
==4723== possibly lost: 27,184 bytes in 31 blocks
==4723== still reachable: 8,352 bytes in 26 blocks
==4723== suppressed: 0 bytes in 0 blocks
After:
==5877== LEAK SUMMARY:
==5877== definitely lost: 0 bytes in 0 blocks
==5877== indirectly lost: 0 bytes in 0 blocks
==5877== possibly lost: 10,800 bytes in 27 blocks
==5877== still reachable: 8,352 bytes in 26 blocks
==5877== suppressed: 0 bytes in 0 blocks
This is now solved by adding the missing free
call.