fix(firstleg): settle zero-package measurements safely

firstleg/src/main/java/com/baiyue/firstleg/mapper/InboundSplitSettlementMapper.java

@@ -205,9 +205,10 @@ public interface InboundSplitSettlementMapper {
 
     @Update("""
         UPDATE fl_inbound_measurement_item
-           SET package_count=#{packageCount},
-               total_volume_cbm=unit_volume_cbm*#{packageCount},
-               volume_weight_kg=volume_weight_kg/NULLIF(package_count,0)*#{packageCount},
+           SET total_volume_cbm=COALESCE(unit_volume_cbm,0)*#{packageCount},
+               volume_weight_kg=CASE WHEN #{packageCount}=0 THEN 0
+                 ELSE COALESCE(volume_weight_kg/NULLIF(package_count,0)*#{packageCount},0) END,
+               package_count=#{packageCount},
                updated_at=CURRENT_TIMESTAMP(3)
          WHERE id=#{measurementItemId} AND tenant_id=#{accountId}
         """)

firstleg/src/test/java/com/baiyue/firstleg/repository/PdaSplitSettlementSqlContractTest.java

@@ -136,6 +136,18 @@ class PdaSplitSettlementSqlContractTest {
             .contains("plan_item.package_count = pick_item.picked_package_count");
     }
 
+    @Test
+    void zeroPackageSettlementNeverWritesNullVolumeWeight() throws Exception {
+        String update = String.join(" ", InboundSplitSettlementMapper.class.getMethod(
+                "updateMeasurementItemForLoaded", long.class, long.class, int.class)
+            .getAnnotation(Update.class).value()).replaceAll("\\s+", " ");
+
+        assertThat(update)
+            .contains("volume_weight_kg=CASE WHEN #{packageCount}=0 THEN 0")
+            .contains("COALESCE(volume_weight_kg/NULLIF(package_count,0)*#{packageCount},0)");
+        assertThat(update.indexOf("volume_weight_kg=")).isLessThan(update.indexOf("package_count=#{packageCount}"));
+    }
+
     @Test
     void keepsAllocationConfirmedUntilReleaseStep() throws Exception {
         String consume = InboundPalletAllocationMapper.class.getMethod("consume",