removing nan from properties query (#906)

Author: AndresOrtegaGuerrero

src/aiidalab_qe/app/utils/search_jobs.py

@@ -85,7 +85,7 @@ def setup_widgets(self):
             </style>
             """
 
-        unique_properties = set(self.df["Properties"].explode())
+        unique_properties = set(self.df["Properties"].explode().dropna())
         unique_properties.discard(None)
         property_checkboxes = [
             ipw.Checkbox(