rql #87988 bug in _simplify with subqueries [validation pending]

local 'select' variable then get overwritten, leading to potential non-simplified code remaining

prioritynormal
typebug
done in0.31.1
load0.300
load left0.000
closed by#de1bbfec40c3 fix simplify for rql w/ subqueries, bad local variable overwrite. Closes #87988