Add input validation for contest and projection files in app.py

- Introduced a new function, is_valid_input, to check if the uploaded files are valid DataFrames and not empty.
- Updated the condition for executing name matching functions to utilize the new validation, enhancing data integrity and user experience.

app.py

@@ -40,6 +40,12 @@ from global_func.create_stack_size_exposures import create_stack_size_exposures
 from global_func.create_general_exposures import create_general_exposures
 from global_func.grab_contest_data import grab_contest_data
 
+def is_valid_input(file):
+    if isinstance(file, pd.DataFrame):
+        return not file.empty
+    else:
+        return file is not None  # For Streamlit uploader objects
+
 player_exposure_format = {'Exposure Overall': '{:.2%}', 'Exposure Top 1%': '{:.2%}', 'Exposure Top 5%': '{:.2%}', 'Exposure Top 10%': '{:.2%}', 'Exposure Top 20%': '{:.2%}'}
 
 tab1, tab2 = st.tabs(["Data Load", "Contest Analysis"])
@@ -112,7 +118,7 @@ with tab1:
                 st.success('Projections file loaded successfully!')
                 st.dataframe(st.session_state['projections_df'].head(10))
         
-    if Contest_file and projections_file:
+    if is_valid_input(Contest_file) and is_valid_input(projections_file):
         st.subheader("Name Matching functions")
         if 'Adj_Contest' not in st.session_state:
             try: