Solve the rest of the compiler warnings.

src/parser/plain_list.rs

@@ -122,7 +122,7 @@ pub fn plain_list<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s s
                     return Err(nom::Err::Error(CustomError::MyError(MyError(
                         "Should be unreachable.",
                     ))));
-                    unreachable!();
+                    // unreachable!();
                 }
             };
         }