Refine position selection logic in hitter tab of Streamlit app

- Updated condition checks for position filtering to simplify logic and enhance clarity.
- Ensured consistent handling of position_var_hitter to improve data filtering functionality for both DraftKings and FanDuel sites.

src/streamlit_app.py

@@ -200,13 +200,15 @@ with hitter_tab:
         
         if team_var_hitter is not None:
             disp_raw = disp_raw[disp_raw['Team'].isin(team_var_hitter)]
-        if position_var_hitter is not None:
+
+        if position_var_hitter:
             if site_var_hitter == 'Draftkings':
                 position_mask = disp_raw['Position'].apply(lambda x: any(pos in x for pos in position_var_hitter))
                 disp_raw = disp_raw[position_mask]
             elif site_var_hitter == 'Fanduel':
                 position_mask = disp_raw['FD_Position'].apply(lambda x: any(pos in x for pos in position_var_hitter))
                 disp_raw = disp_raw[position_mask]
+
         st.session_state['hitter_disp_frame'] = disp_raw
     elif table_var_hitter == 'Active Baselines':
         disp_raw = hitter_info
@@ -214,7 +216,7 @@ with hitter_tab:
         if team_var_hitter is not None:
             disp_raw = disp_raw[disp_raw['Team'].isin(team_var_hitter)]
         
-        if position_var_hitter is not None:
+        if position_var_hitter:
             if site_var_hitter == 'Draftkings':
                 position_mask = disp_raw['Position'].apply(lambda x: any(pos in x for pos in position_var_hitter))
                 disp_raw = disp_raw[position_mask]