Remove potential Attribute error from __origin__

Author: FayeDel

discord_slash/model.py

@@ -484,10 +484,10 @@ def from_type(cls, t: type):
             return cls.ROLE
         if hasattr(typing, "_GenericAlias"):  # 3.7 onwards
             # Easier than imports
-            if (
-                t.__origin__ is not None and t.__origin__ is typing.Union
-            ):  # proven in 3.7.8+, 3.8.6+, 3.9+ definitively
-                return cls.MENTIONABLE
+            if hasattr(t, "__origin__"):
+                if t.__origin__ is typing.Union:
+                    # proven in 3.7.8+, 3.8.6+, 3.9+ definitively
+                    return cls.MENTIONABLE
         if not hasattr(typing, "_GenericAlias"):  # py 3.6
             if isinstance(t, typing._Union):  # noqa
                 return cls.MENTIONABLE