Fix while loop to create a random program in stochastic algorithms

[nicolaefilat]

The issues lies here:

HerbSearch.jl/src/stochastic_iterator.jl

Lines 74 to 84 in c8cdb1c

	dmap = mindepth_map(grammar)
	sampled_program = rand(RuleNode, grammar, iter.sym, max_depth) #TODO: replace iter.sym with a domain of valid rules
	substitute!(solver, Vector{Int}(), sampled_program)
	while !isfeasible(solver)
	#TODO: prevent infinite loops here. Check max_time and/or max_enumerations.
	sampled_program = rand(RuleNode, grammar, iter.sym, max_depth) #TODO: replace iter.sym with a domain of valid rules
	substitute!(solver, Vector{Int}(), sampled_program)
	end
	return (sampled_program, IteratorState(sampled_program, iter.initial_temperature,dmap))