At function ExtendBufferedRelShared, has a always true test.
eb.rel was dereferenced one line above, so in
if (eb.rel) is always true.
I think it's worth removing the test, because Coverity raises dozens of alerts thinking eb.rel might be NULL.
Besides, one less test is one less branch.
This also happens in ExtendBufferedRelTo, and the comment there explains that the eb.rel 'could have been closed while waiting for lock'. So for the same consideration, the test in ExtendBufferedRelShared might be still needed? But I'm not familiar with the arounding codes, so need someone else to confirm that.
