Resolve "Lacking sanity checks to iricdata connection"

Closes #21 (closed)

pyiricdata/Client.py

@@ -309,11 +309,16 @@ class Client:
     """
     def filter_datafiles(self, term, field='filename', exact_match=False, **kwargs):
         df = self.get_datafiles_list(**kwargs)
-
-        if exact_match:
-            return df[df[field].str.fullmatch(term)]
+        if df is None:
+            sys.stderr.write("Please try again with more arguments, for more details please see function get_datafiles_list()")
+            return None
+        elif df.empty:
+            return None
         else:
-            return df[df[field].str.contains(term)]
+            if exact_match:
+                return df[df[field].str.fullmatch(term)]
+            else:
+                return df[df[field].str.contains(term)]
 
     """ Get file content according to file_id """
     def get_file(self, file_id):