fix(browser): should check whether process exists

Closes #325.

browser.js

@@ -144,7 +144,7 @@ function load() {
  } catch(e) {}
 
  // If debug isn't set in LS, and we're in Electron, try to load $DEBUG
- if ('env' in (process || {})) {
+ if ('env' in (typeof process === 'undefined' ? {} : process)) {
  r = process.env.DEBUG;
  }