Add error handling for data loading

app.py

@@ -113,7 +113,17 @@ def prepare_data():
         'right_rot': right_rot
     }
 
-plot_data = prepare_data()
+try:
+    plot_data = prepare_data()
+except Exception as e:
+    print(f"Error preparing plot data: {e}")
+    plot_data = {
+        'times': [],
+        'left_pos': {'x': [], 'y': [], 'z': []},
+        'left_rot': {'yaw': [], 'pitch': [], 'roll': []},
+        'right_pos': {'x': [], 'y': [], 'z': []},
+        'right_rot': {'yaw': [], 'pitch': [], 'roll': []}
+    }
 
 METRIC_LABELS = {
     "x_cm": "X (cm)",
@@ -232,20 +242,35 @@ CUSTOM_CSS = """
 
 def build_plot_fig(metric: str, hand: str = "left") -> go.Figure:
     """Build Plotly figure for a metric."""
-    times = plot_data['times']
-    
-    if hand == "left":
-        if "cm" in metric:
-            data = plot_data['left_pos'][metric.replace('_cm', '')]
-        else:
-            data = plot_data['left_rot'][metric.replace('_deg', '')]
-        name = "Left Hand"
-    else:
-        if "cm" in metric:
-            data = plot_data['right_pos'][metric.replace('_cm', '')]
+    try:
+        times = plot_data.get('times', [])
+        
+        if hand == "left":
+            if "cm" in metric:
+                key = metric.replace('_cm', '')
+                data = plot_data.get('left_pos', {}).get(key, [])
+            else:
+                key = metric.replace('_deg', '')
+                data = plot_data.get('left_rot', {}).get(key, [])
+            name = "Left Hand"
         else:
-            data = plot_data['right_rot'][metric.replace('_deg', '')]
-        name = "Right Hand"
+            if "cm" in metric:
+                key = metric.replace('_cm', '')
+                data = plot_data.get('right_pos', {}).get(key, [])
+            else:
+                key = metric.replace('_deg', '')
+                data = plot_data.get('right_rot', {}).get(key, [])
+            name = "Right Hand"
+        
+        if not times or not data:
+            # Return empty plot
+            times = [0]
+            data = [0]
+    except Exception as e:
+        print(f"Error in build_plot_fig: {e}")
+        times = [0]
+        data = [0]
+        name = "Error"
     
     fig = go.Figure()
     fig.add_trace(