Fix contable memory leak when a dict contains no connectors
Fix contable memory leak when a dict contains no connectors

Also remove redundant recomputation of the number of connectors.

opencog/link-grammar,opencog/link-grammar,linas/link-grammar,opencog/link-grammar,ampli/link-grammar,opencog/link-grammar,linas/link-grammar,opencog/link-grammar,ampli/link-grammar,ampli/link-grammar,linas/link-grammar,opencog/link-grammar,ampli/link-grammar,linas/link-grammar,opencog/link-grammar,linas/link-grammar,ampli/link-grammar,linas/link-grammar,linas/link-grammar,opencog/link-grammar,opencog/link-grammar,linas/link-grammar,linas/link-grammar,ampli/link-grammar,ampli/link-grammar,ampli/link-grammar,ampli/link-grammar