Catch PFP not found error

menu.py

@@ -1,11 +1,15 @@
 # From https://docs.streamlit.io/develop/tutorials/multipage/st.page_link-nav
 import streamlit as st
+import os
 import project_config
 
 def authenticated_menu():
 
     # Insert profile picture
-    st.sidebar.image(str(project_config.MEDIA_DIR / 'pfp' / f"{st.session_state.profile_pic}.png"), use_column_width=True)
+    pfp_path = str(project_config.MEDIA_DIR / 'pfp' / f"{st.session_state.profile_pic}.png")
+    if not os.path.exists(pfp_path):
+        pfp_path = str(project_config.MEDIA_DIR / 'pfp' / "gravity.png")
+    st.sidebar.image(pfp_path, use_column_width=True)
     st.sidebar.markdown("---")
 
     # Show a navigation menu for authenticated users