I don't quite understand. When you say "That would be because the theory of evolution doesn't apply when life doesn't exist.", are you saying that 1.no life existed before earth, OR 2.that evolution theory only applies to earth? Well, or both. Just trying to understand.
He's saying that evolution explains what happens when life reproduces. Thus, before any life exists, evolution doesn't apply, doesn't exist, doesn't happen.
It's kind of like weather not happening when there's not an atmosphere. Weather is the way that an atmosphere changes over time. Evolution is the way that living things change over time (i.e., across generations).
In slightly more technical terms the process of evolution happens any time the following three things are all present: 1) reproduction, 2) (inheritable) variation, 3) selection. Before life came about, #1 (reproduction) did not exist, and thus the process of evolution did not take place. Only after the first reproducing thing (it probably didn't rise to the level of "life" yet) came into existence, by whatever means, did evolutionary processes occur.
I think there could be life on other planets. I think there could be life on other planets pre-earth, now, and post-earth. I don't think life is limited to earth. But, you know, who knows for sure - not me.