Maker: Don't show error overlay when running empty program

[islemaster]

Maker used to display its connection failure overlay when running an empty program, even connection to the board normally succeeds. Now it runs the empty program without complaint.

Before	After

Root cause

Because JavaScript empty string "" is falsy, App Lab was not creating an Interpreter at all for empty programs. When this happened with Maker enabled, board connection would fail because part of the connection process is injecting board components into the interpreter, and Maker always assumed it was passed a valid interpreter.

After this change, App Lab does create an interpreter for empty programs, which seems like correct behavior to me (there should always be an interpreter if App Lab is "running"). This also has a subtle effect on the debug console, which I would also consider a bugfix:

Before	After

Follow-up work

We might also be able to remove this conditional from Applab.onTick but I wanted to start with the minimum change to fix this issue first.