Fixes error identifier collision in getState

[mediabounds]

error is already defined in this scope which causes the uglifier (when building the Adapt course) to incorrectly mangle the variables in this function leading to a JavaScript error when restoring state.

FWIW, here's a screenshot of the final course output before this fix is applied.

The callback error parameter is mangled as n, but the callback function checks for the existence of an l variable, which doesn't exist, causing an execution error.

[brian-learningpool]

Thanks @mediabounds!