Photo: Jason McDonald/Searchlight Pictures Is This Thing On? is much more about a relationship than it is about comedy, which is probably a good thing, given how difficult it is to make movies about stand-up. Fictional comics on screen tend to skew toward being tortured truth-tellers or delusional sociopaths or both, but Alex Novak, played by Will Arnett, is neither. He’s a finance guy who recently split from his wife of 20 years, and who stumbles into an open mic night on a whim while trying