eliminate duplicate placeholders in "walkComparison" function within QueryExpressionVisitor

I've run into an issue when using Criteria with QueryBuilder when Criteria uses multiple checks on same variable in different context, example:
field1 = value OR (field1 in values AND field2 = true)... what happens is field 1 placeholder is duplicated, and an error occures in code complaining about invalid # of parameters.  The fix eliminates this issue, making sure parametername is unique.

I have not had time to check any other possible issues this may cause, but a review of the code doesn't appear to impact any other function.