pymcnp: fixed compile issues 4

Author: BitterB0NG0

src/pymcnp/inp/card_surface.py

@@ -105,5 +105,5 @@ def to_mcnp(self):
         """
 
         return _parser.postprocess_continuation_line(
-            f'{self.prefix or ''}{self.number} {self.transform or ''} {self.option}'
+            f'{self.prefix or ""}{self.number} {self.transform or ""} {self.option}'
         )

src/pymcnp/utils/types.py

@@ -713,7 +713,7 @@ def to_mcnp(self) -> str:
             return f'{self.z:03}{self.a:03}'
 
 
-class Particle(_object.McnpElement_, enum.StrEnum):
+class Particle(_object.McnpElement_, enum.Enum):
     """
     Represents MCNP particle designators.
     """