wasm-interp: Fix off-by-one in DoThrow

[SoniEx2]

No description provided.

[sbc100]

No test output changed as the result of this? Would writing a test for this be tricky?

I don't really know this code myself but the change looks reasonable.

[SoniEx2]

yeah upstream doesn't have tests for this.

uh hmm... we're not sure how to trigger this, maybe something like

throw
try
catch
end

?

[SoniEx2]

(yep:

  +out/test/regress/interp-throw-before-try.txt:15: expected an exception to be thrown
  +1/2 tests passed.

)

[SoniEx2]

@sbc100