Using Processing-0177 on Mac OS X.

e.g. call dataPath() with no arguments in setup() - or any other similar error.

Thanks for the report, I'll opt not to fix this, but here's the rationale
for posterity:

1) The emulator launches as the build starts. Both processes take a long
time, but are independent, making them suitable to start in parallel. If we
instead waited to see if the build failed, we'll have to do things
sequentially, which will make builds run more slowly.

2) If you're running a sketch and get a compile error, chances are that's
not gonna keep you from continuing Android development. In fact, it's more
efficient to have the emulator up and running, since it'll be ready to go
when you've fixed the error.

3) Because of the crazy amount of overhead on booting/starting the
emulator, we're keeping a single emulator instance open during the P5
session (until the user closes it, or closes Processing). So it'll seem
less weird over time.