not sure, maybe it's just the same colour as the background?

probably i could have a blank reaction i don't think you can pick them in nostrudel, though i guess you could probably paste in a NBSP (there's about a dozen of them) 

 more likely your device doesn't have the character in the font 

 oh, i see, that was you... haha... 

it's probably a literal space character in the content field of a kind 7