Conditional assignment fails with object literals

[jussiry]

foo ?=
  bar: true
  baz: false

compiles quite unexpectedly to:

if (typeof foo === "undefined" || foo === null) {
  foo = {
    bar: true
  };
}
({
  baz: false
});

Adding parenthesis makes it work again, but since normal assignment works also without parenthesis this can easily result in strange errors in code.

[michaelficarra]

Duplicate of #1961 and #1974, fixed by 62a331a on master. Related: #2135

[jussiry]

Quick work, good to hear it's already fixed for next version. :)