Add test for processing empty section

nomad/normalizing/metainfo.py

@@ -47,16 +47,11 @@ class MetainfoNormalizer(Normalizer):
         logger = logger.bind(normalizer=self.__class__.__name__)
         self.logger = logger
 
-        if self.entry_archive.data:
-            sections = list(self.entry_archive.data.m_traverse())
-            if sections:
+        for sub_section in self.entry_archive.m_contents():
+            if isinstance(sub_section, EntryData):
+                sections = list(sub_section.m_traverse())
                 for section, _, _ in sections:
                     self.normalize_section(section, logger)
-            else:
-                self.normalize_section(self.entry_archive.data, logger)
-
-        for sub_section in self.entry_archive.m_contents():
-            if not isinstance(sub_section, EntryData):
-                self.normalize_section(sub_section, logger)
+            self.normalize_section(sub_section, logger)
 
         self.normalize_section(self.entry_archive, logger)