Update app.py

app.py

@@ -9,7 +9,7 @@ exts = list(df["extension"].unique())
 
 def compute(lang):
     df_lang = df[df["language"]==lang]
-    df_lang["extension"] = df["extension"].fillna(" ")
+    df["extension"].fillna("[no ext]", inplace=True)
     # clean up weird exts
     df_lang = df_lang[df_lang["ext_fraction_per_lang"] > 0.0001].reset_index()