Appying changes proposed by abministrators

Author: Javier Duran

astroquery/esa/xmm_newton/core.py

@@ -423,9 +423,9 @@ def get_epic_spectra(self, filename, source_number, *,
 
         except FileNotFoundError:
             log.error("File %s not found" % (filename))
-            return None
+            return
 
-        if ret is None or ret == {}:
+        if not ret:
             log.info("Nothing to extract with the given parameters:\n"
                      "  PPS: %s\n"
                      "  Source Number: %u\n"