safety fix in pxyimport

pyximport/pyximport.py

@@ -205,7 +205,7 @@ class PyxImporter(object):
         try:
             fp, pathname, (ext,mode,ty) = imp.find_module(fullname,package_path)
             if fp: fp.close()  # Python should offer a Default-Loader to avoid this double find/open!
-            if pathname.endswith(self.extension):
+            if pathname and pathname.endswith(self.extension):
                 return PyxLoader(fullname, pathname,
                                  pyxbuild_dir=self.pyxbuild_dir)
             if ty != imp.C_EXTENSION: # only when an extension, check if we have a .pyx next!