debug plugin causes console statements to throw

[ewoerner]

In multiple circumstances, the debug plugin throws errors.

Example: console.log(window)

Uncaught RangeError: Maximum call stack size exceeded
    at JSON.stringify (<anonymous>)
    at <anonymous>:60:16
    at Array.forEach (<anonymous>)
    at debugTab.console.renderLine (<anonymous>:57:8)
    at debugTab.console.log (<anonymous>:86:20)
    at window.console.<computed> [as log] (<anonymous>:110:31)
    at <anonymous>:1:9

See also bannergress/iitc-plugin#34

In general, the contract of console.something() is that it must never throw.