diff --git a/src/calibre/gui2/library/delegates.py b/src/calibre/gui2/library/delegates.py
index a2f679e475..0be684247e 100644
--- a/src/calibre/gui2/library/delegates.py
+++ b/src/calibre/gui2/library/delegates.py
@@ -145,6 +145,8 @@ def make_clearing_spinbox(spinbox):
             if ev.key() == Qt.Key.Key_Space:
                 self.clear_to_undefined()
             else:
+                if self.value() == self.minimum():
+                    self.clear()
                 return spinbox.keyPressEvent(self, ev)
     return SpinBox
 
diff --git a/src/calibre/gui2/library/models.py b/src/calibre/gui2/library/models.py
index 6aa176292a..4ab816e90a 100644
--- a/src/calibre/gui2/library/models.py
+++ b/src/calibre/gui2/library/models.py
@@ -117,7 +117,7 @@ class ColumnIcon(object):  # {{{
                                     template_cache=template_cache)
                 if not rule_icons:
                     continue
-                icon_list = [ic.strip() for ic in rule_icons.split(':')]
+                icon_list = [ic.strip() for ic in rule_icons.split(':') if ic.strip()]
                 icons.extend(icon_list)
                 if icon_list and not kind.endswith('_composed'):
                     break