search all array elements for [draw] event callbacks for nested structs

This fixes [draw] event callbacks for nested ds arrays.

The previous attempt didn't iterate through the outer array elements to find the relevant inner array.

This has the unfortunate side-effect of scaling horribly. Probably not a big deal for clicks, but definitely not good for "drag" events and complex nested data structures.

Events for non-nested arrays will continue to have decent performance-- the index into the array is cached GUI side so in that case there's no array iteration necessary.