Fix crash with update check on Linux

[FredrikAugust]

Did you search for similar issues before submitting this one?
Yes, couldn't find any related issues.

Describe the issue you encountered:
Browser opens with error and then crashes.

Error when opening:

TypeError: Error processing argument at index 0, conversion failure from null
    at TypeError (native)
    at Object.exports.init.err [as init] (/usr/share/brave/resources/app.asar/app/updater.js:98:17)
    at PackageLoader.load (/usr/share/brave/resources/app.asar/app/index.js:733:15)
    at fs.readFile (/usr/share/brave/resources/app.asar/app/package-loader.js:16:5)
    at ELECTRON_ASAR.js:492:9
    at FS.ReqWrap.wrapper [as oncomplete] (fs.js:681:17)
Failed to get crash dump id.
Report Id: OK

Message on crash:

[1]    10301 floating point exception (core dumped) brave

Expected behavior:
No crashes.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Fedora 24 (Linux v.4.5.5 64-bit)
• Brave Version:
  0.12.0
• Steps to reproduce:
  1 Just browse around
  Error message should be more useful on app/updater.js:98 #1980