guess_type: if the type is optional, treat it like it's "not None" (#…

…3839)

* guess_type: if the type is optional, treat it like it's "not None"

When guessing the type for an Optional annotation, the Optional was already
being stripped off, but this value was being ignored, except for error
messages. So actually use the Optional-stripped value.

* Strip Optional when casting Var .to

reflex/ivars/base.py

@@ -362,7 +362,11 @@ def to(
         from .object import ObjectVar, ToObjectOperation
         from .sequence import ArrayVar, StringVar, ToArrayOperation, ToStringOperation
 
-        fixed_type = get_origin(var_type) or var_type
+        base_type = var_type
+        if types.is_optional(base_type):
+            base_type = types.get_args(base_type)[0]
+
+        fixed_type = get_origin(base_type) or base_type
 
         fixed_output_type = get_origin(output) or output