fix: multiple mismatched-type-assignment fixes (#4482)

* fix: only make type optional if it's not already, add helper to unwrap rx.Field

* migrate unwrap_field_type to private function

reflex/state.py

@@ -104,6 +104,7 @@ from reflex.utils.serializers import serializer
 from reflex.utils.types import (
     _isinstance,
     get_origin,
+    is_optional,
     is_union,
     override,
     value_inside_optional,
@@ -278,6 +279,22 @@ if TYPE_CHECKING:
     from pydantic.v1.fields import ModelField
 
 
+def _unwrap_field_type(type_: Type) -> Type:
+    """Unwrap rx.Field type annotations.
+
+    Args:
+        type_: The type to unwrap.
+
+    Returns:
+        The unwrapped type.
+    """
+    from reflex.vars import Field
+
+    if get_origin(type_) is Field:
+        return get_args(type_)[0]
+    return type_
+
+
 def get_var_for_field(cls: Type[BaseState], f: ModelField):
     """Get a Var instance for a Pydantic field.
 
@@ -288,16 +305,12 @@ def get_var_for_field(cls: Type[BaseState], f: ModelField):
     Returns:
         The Var instance.
     """
-    from reflex.vars import Field
-
     field_name = format.format_state_name(cls.get_full_name()) + "." + f.name
 
     return dispatch(
         field_name=field_name,
         var_data=VarData.from_state(cls, f.name),
-        result_var_type=f.outer_type_
-        if get_origin(f.outer_type_) is not Field
-        else get_args(f.outer_type_)[0],
+        result_var_type=_unwrap_field_type(f.outer_type_),
     )
 
 
@@ -1313,8 +1326,8 @@ class BaseState(Base, ABC, extra=pydantic.Extra.allow):
 
         if name in fields:
             field = fields[name]
-            field_type = field.outer_type_
-            if field.allow_none:
+            field_type = _unwrap_field_type(field.outer_type_)
+            if field.allow_none and not is_optional(field_type):
                 field_type = Union[field_type, None]
             if not _isinstance(value, field_type):
                 console.deprecate(