ternary operator ? : expect a bool expression before "?"
ta.dev(bar_hh, 2) - returns float, not a bool
so make smth like that

float bar_h1 = ta.dev(bar_hh, 2) > 0 ? na : bar_hh

or

float bar_h1 = ta.dev(bar_hh, 2) != 0 ? na : bar_hh

or any bool expression you need