fix NoneType math

src/plant_transaction_data/service.py

@@ -15,6 +15,16 @@ from src.auth.service import CurrentUser
 logger = logging.getLogger(__name__)
 
 
+def _safe_float(x: object) -> float:
+    """Safely convert `x` to float, returning 0.0 for None or invalid values."""
+    try:
+        if x is None:
+            return 0.0
+        return float(x)
+    except Exception:
+        return 0.0
+
+
 async def get(
     *, db_session: DbSession, transaction_data_id: str
 ) -> Optional[PlantTransactionData]:
@@ -67,12 +77,12 @@ async def get_charts(
 
     for idx, item in enumerate(chart_data):
         total_cost = (
-            float(item.chart_capex_annualized)
-            + float(item.chart_oem_annualized)
-            + float(item.chart_fuel_cost_annualized)
-            + float(item.cost_disposal_cost)
+            _safe_float(item.chart_capex_annualized)
+            + _safe_float(item.chart_oem_annualized)
+            + _safe_float(item.chart_fuel_cost_annualized)
+            + _safe_float(item.cost_disposal_cost)
         )
-        revenue = float(item.chart_revenue_annualized)
+        revenue = _safe_float(item.chart_revenue_annualized)
 
         if previous_total_cost is not None and previous_revenue is not None:
             prev_diff = previous_total_cost - previous_revenue