Fix a bug in AndBIT::is_argument_of
Fix a bug in AndBIT::is_argument_of

The last argument of a precondition should not be discarded.

inflector/atomspace,misgeatgit/atomspace,misgeatgit/atomspace,misgeatgit/atomspace,AmeBel/atomspace,rTreutlein/atomspace,AmeBel/atomspace,yantrabuddhi/atomspace,AmeBel/atomspace,ArvinPan/atomspace,rTreutlein/atomspace,ArvinPan/atomspace,yantrabuddhi/atomspace,rTreutlein/atomspace,inflector/atomspace,inflector/atomspace,AmeBel/atomspace,misgeatgit/atomspace,rTreutlein/atomspace,ArvinPan/atomspace,yantrabuddhi/atomspace,ArvinPan/atomspace,misgeatgit/atomspace,AmeBel/atomspace,yantrabuddhi/atomspace,rTreutlein/atomspace,inflector/atomspace,yantrabuddhi/atomspace,inflector/atomspace