MINOR: [Go] check nil buffer in SizeInBytes

[Yifeng-Sigma]

Rationale for this change

Saw a nil error. Unclear to me how this nil buffer got constructed, because when building the arrow data we seem to already check it. But we should do a nil check here anyway

What changes are included in this PR?

Added a nil check.

Are these changes tested?

Are there any user-facing changes?

No.

[github-actions]

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[zeroshade]

Looks good to me, can you add a unit test for this?

[Yifeng-Sigma]

Looks good to me, can you add a unit test for this?

I tried but didn't figure out a way to build with nil buffer.
in NewData() we checked nil buffers.

[zeroshade]

Creating an Array with no null values should produce something with a nil validity bitmap. Alternately you should be able to use NewData to create a Data object passing []*memory.Buffer{nil, buffer} since it's valid to have a nil validity bitmap if there are no nulls. I'll see if i can put together a unit test that reproduces the original crash that I can add for you

[zeroshade]

@Yifeng-Sigma Adding the following to data_test.go will provide a test that should fail without this change and should succeed with this change:

[Yifeng-Sigma]

@Yifeng-Sigma Adding the following to data_test.go will provide a test that should fail without this change and should succeed with this change:

Thanks! added to the PR.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 6 benchmarking runs that have been run so far on merge-commit 77e572b.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 49 possible false positives for unstable benchmarks that are known to sometimes produce them.