[legacy-framework] Fix crash when using Blitz inside iframes

[mtford90]

Closes blitz-js/legacy-framework#111

[markhughes]

Also seems recommended on MDN:

setItem() may throw an exception if the storage is full. Particularly, in Mobile Safari (since iOS 5) it always throws when the user enters private mode. (Safari sets the quota to 0 bytes in private mode, unlike other browsers, which allow storage in private mode using separate data containers.) Hence developers should make sure to always catch possible exceptions from setItem().

see: https://developer.mozilla.org/en-US/docs/Web/API/Storage/setItem

[flybayer]

Sweet, thanks!!