fix nan extension

app.py

@@ -13,12 +13,13 @@ tags = {}
 for index, row in df.iterrows():
     if row["language"] not in tags:
         tags[row["language"]] = []
-    tags[row["language"]].append(row["extension"])
+    tags[row["language"]].append(str(row["extension"]))
 all_languages = list(tags.keys())
 
 
 @st.cache(max_entries=100)
 def load_data(language, ext, min_alphanum, max_line_length, max_mean_line_length, non_lexable):
+    ext = None if ext == "nan" else ext
     samples = load_dataset(
         "loubnabnl/the-stack-inspection-data",
         data_dir=f"data/{language}/{ext}",