left_connector_list_update(): Bug fix - ub may be too big
left_connector_list_update(): Bug fix - ub may be too big

It may be equal to sent_length, and refer beyond the end of
the l_table (will actually refer to r_table[0]).

Because it refers to a valid address, no memory access fault may happen.
It is also undetected by ASAN etc.

In principle it may cause wrong results due to the lookup in the wrong
table.

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