`this`-type for choice results in error clazz

[fridis]

This commit added workarounds to option.fz and outcome.fz for a crash in the middle end (error clazz found) when running tests/choice_inheritance:

-    auto_unwrap T (try option.this)
+    auto_unwrap T (try (option T)) /* NYI: BUG: auto_unwrap T (try option.this) */