fix: Fixes crashes when estimating pressures with a filter pressure drop.

Sources/EstimatedPressureDependency/Key.swift

@@ -143,46 +143,48 @@ extension EstimatedPressureDependency {
       )
     }
   }
+  
+  private func setFilterPressureDrop(
+    _ filterDrop: Positive<Double>,
+    measurement: inout EquipmentMeasurement
+  ) {
+    switch measurement {
+    case var .airHandler(airHandler):
+      airHandler.postFilterPressure = airHandler.returnPlenumPressure +
+      filterDrop.positiveValue
+      measurement = .airHandler(airHandler)
+    case var .furnaceAndCoil(furnace):
+      furnace.postFilterPressure = furnace.returnPlenumPressure + filterDrop.positiveValue
+      measurement = .furnaceAndCoil(furnace)
+    }
+  }
 
   public func estimatedPressure(
     equipmentMeasurement: EquipmentMeasurement,
     airflow updatedAirflow: Positive<Double>,
-    filterPressureDrop: Positive<Double>
+    filterPressureDrop: Positive<Double>?
   ) async throws -> EquipmentMeasurement {
-    let estimate = try await estimatedPressure(
+    var estimate = try await estimatedPressure(
       equipmentMeasurement: equipmentMeasurement,
       airflow: updatedAirflow.positiveValue
     )
-
-    switch estimate {
-
-    case var .airHandler(airHandler):
-      airHandler.postFilterPressure = airHandler.returnPlenumPressure + filterPressureDrop.positiveValue
-      return .airHandler(airHandler)
-
-    case var .furnaceAndCoil(furnaceAndCoil):
-      furnaceAndCoil.postFilterPressure = furnaceAndCoil.returnPlenumPressure + filterPressureDrop.positiveValue
-      return .furnaceAndCoil(furnaceAndCoil)
-    }
+    guard let filterPressureDrop else { return estimate }
+    setFilterPressureDrop(filterPressureDrop, measurement: &estimate)
+    return estimate
   }
   
   public func estimatedPressure(
     equipmentMeasurement: EquipmentMeasurement,
     airflow updatedAirflow: Double,
-    filterPressureDrop: Positive<Double>?
+    filterPressureDrop: Double?
   ) async throws -> EquipmentMeasurement {
-    guard let filterPressureDrop else {
-      return try await estimatedPressure(
-        equipmentMeasurement: equipmentMeasurement,
-        airflow: updatedAirflow
-      )
-    }
-    return try await estimatedPressure(
+    try await estimatedPressure(
       equipmentMeasurement: equipmentMeasurement,
-      airflow: updatedAirflow,
-      filterPressureDrop: Positive(filterPressureDrop.positiveValue)
+      airflow: Positive(updatedAirflow),
+      filterPressureDrop: filterPressureDrop != nil ? Positive(filterPressureDrop!) : nil
     )
   }
+
 }
 
 extension EstimatedPressureDependency: DependencyKey {