Segfault on clear() on default-constructed CompressedMatrix

[Joel Croteau]

23672f6 subtly altered the behavior of CompressedMatrix on initialization. Previously, it had been safe to call clear() on a CompressedMatrix that had been default-constructed before calling resize(), now this causes a segfault, which breaks existing library code. I have created a fork with a fix here but it appears that you do not allow outside pull requests.

[Klaus Iglberger]

Hi Joel!

Thanks a lot for pointing out this defect. We are very sorry for the inconvenience, but apparently, despite a month of running tests, this one slipped through.

We have used your pull request to fix the problem for row-major compressed matrices and additionally applied the fix for column-major compressed matrices. Also, we have added the according tests to assert the error will not happen again.

Thanks again, your help is highly appreciated!

Best regards,

Klaus!

[Klaus Iglberger]

The fix has been implemented and verified via tests. It is immediately available via cloning the Blaze repository and will be officially released in Blaze 3.1.