Fix segfault for 1-qubit QUnit GetProbs()

5fa8e96 introduced a segmentation fault in QUnit::GetProbs() (QrackSimulator.out_probs()) in the specific case that the QUnit instance has exactly 1 qubit. I estimate the severity of the vulnerability to be low: all tests so far have resulted in a "caught" segmentation fault rather than a silent one, likely because the first unsafe access to memory is always an attempt to write to memory address 0/NULL. The specific case of calling QUnit::GetProbs() for an instance with just one qubit is likely also uncommon in user code. With that said, please update immediately!

(Thanks to @cosenal for catching this!)

Full Changelog:
unitaryfund/qrack@vm6502q.v9.12.34...vm6502q.v9.12.38
unitaryfund/pyqrack@v1.32.28...v1.32.29
v0.10.18...v0.10.19

sha1sum results:
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