TokenList unsafely handles potentially undefined return type

[kumavis]

https://github.com/MetaMask/controllers/blob/502bb2639ebc2a0b695671166f6747761e08795f/src/assets/TokenListController.ts#L271-L273

[kumavis]

typescript failing to save us bc typecasting
does typescript have templating/abstract types?

safelyExecute<Token[]>(() => ...)

or something crazier like

async function safelyExecuteWithTimeout(operation T) returnTypeOf(T) {...}

[desi]

We should stop the use of this function so we will close this one and #543 will cover it.