Don't load shp from sentinel

Author: JamesParrott

shapefile.py

@@ -1115,14 +1115,12 @@ def __init__(
                     self.load(path)
                     return
 
-        self.shp = self._seek_0_on_file_obj_wrap_or_open_from_name("shp", shp)
-        self.dbf = self._seek_0_on_file_obj_wrap_or_open_from_name("dbf", dbf)
-
-        if shp is _NoShpSentinel:
-            self.shx = None
-        else:
+        if shp is not _NoShpSentinel:
+            self.shp = self._seek_0_on_file_obj_wrap_or_open_from_name("shp", shp)
             self.shx = self._seek_0_on_file_obj_wrap_or_open_from_name("shx", shx)
 
+        self.dbf = self._seek_0_on_file_obj_wrap_or_open_from_name("dbf", dbf)
+
         # Load the files
         if self.shp or self.dbf:
             self._try_to_set_constituent_file_headers()