Uncaught (in promise) TypeError: object null is not iterable ... at getCompilerVersion

[gpersoon]

@todo

• fix selected compiler version when pragma solidity statement is missing
• fix error when pragma solidity... includes more than one whitespace after "pragma"

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While testing the solution for #15 I noticed the following.
If the source code doesn't exactly contain the text "pragma solidity....;" then the following error is shown in the console:

Uncaught (in promise) TypeError: object null is not iterable (cannot read property Symbol(Symbol.iterator))
    at getCompilerVersion (bundle.js:36108)

and the source code isn't saved.

This is related to:

https://github.com/ethereum-play/editor-solidity/blob/master/src/node_modules/getCompilerVersion.js
var regex = /pragma solidity\s*([><=\^]*)\s*(\d+\.\d+\.\d+)?\s*([><=\^]*)\s*(\d+\.\d+\.\d+)?;/

So if you've made a typo, or even haven't added "pragma solidity ..;" (e.g. delete everything and start typing), then the source can be lost.
Also if you have two spaces between "pragma" and "solidity", the problem also occurs and the source doesn't compile:

"pragma  solidity ..;

(this can be solved be changing the regex)