bugfix of the bugfix - should really write tests first

src/icartt/dataset.py

@@ -214,10 +214,14 @@ class KeywordComment:
 class StandardNormalComments(collections.UserList):
     @property
     def nlines(self):
-        n = 1 # shortnames line, and keywords might be multiline...
-        n += len(self.freeform)
-        n += sum(len(k.data[0].split("\n")) or 1 for k in self.keywords.values())
-        # was: len(self.freeform) + 1 + sum([len(k.data) for k in self.keywords.values()])
+        """calculates the number of lines in the normal comments section"""
+        n = 1 # shortnames line
+        n += len(self.freeform) # freeform comment
+        for k in self.keywords.values():
+            try:
+                n += len(k.data[0].split("\n")) # and keywords might be multiline...
+            except IndexError: # ok we have no list,
+                n += 1 # just add 1
         return n
 
     @property