Removed unused code

Author: SilkeSchomann

src/mslice/models/cut/cut.py

@@ -142,8 +142,6 @@ def width(self, width_str):
                     self._width = float(width_str)
                 except ValueError:
                     raise ValueError("Invalid width")
-        elif width_str == "":
-            self._width = self.end - self.start
         else:
             self._width = None