Do not cast bytes to strs

src/grung/types.py

@@ -343,8 +343,9 @@ class TextFilePointer(BinaryFilePointer):
     extension: str = ".txt"
 
     def prepare(self, data: value_type):
-        if data and not isinstance(data, bytes):
-            return str(data).encode()
+        if isinstance(data, bytes):
+            return data
+        return str(data).encode()
 
     def deserialize(self, value: str, db: TinyDB, recurse: bool = True) -> value_type:
         if not value: