Maybe expression (feature `maybe_expr`) not supported.

[ShawnMcCool]

The maybe_expr feature appears to not be supported. Perhaps this PR could resolve it?

#1005

[kvakvs]

I believe I merged the contribution by @zyuyou some weeks ago, but was it released since then? I do not control that.

[ignatov]

updated in 0.11.1197, https://plugins.jetbrains.com/plugin/7083-erlang/versions/stable/327858