Update sancov.c

[bryonglodencissp]

[../honggfuzz-master/sancov.c:454]: (error) Common realloc mistake: 'mapsBuf' nulled but not freed upon failure

This solution from Stack Overflow was helpful in fixing the error because if realloc cannot find enough space, it returns a null pointer, and leaves the previous region allocated.

Found by https://github.com/bryongloden/cppcheck

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[bryonglodencissp]

I signed it!

[googlebot]

CLAs look good, thanks!

[robertswiecki]

Thanks, good catch. I decided to solve it everywhere :) f49962d