Fix some other scan coverity reports
Fix several small errors as determined by the Coverity scan.

One potential NULL dereference, but mostly checks for return values
from SMARTS calls.
Merge pull request #64 from ghutchis/FIX_descriptor-coverity-errors

Fix several small errors as determined by the Coverity scan.
Merge pull request #50 from serval2412/master

Fix some other scan coverity reports