Prevent crashing when DataStack is deallocated ahead of ListMonitor and child objects

Sources/From.swift

@@ -140,8 +140,16 @@ public struct From<D: DynamicObject> {
     }
     
     internal func applyToFetchRequest<U>(_ fetchRequest: CoreStoreFetchRequest<U>, context: NSManagedObjectContext, applyAffectedStores: Bool = true) throws {
-        
-        fetchRequest.entity = context.parentStack!.entityDescription(for: EntityIdentifier(self.entityClass))!
+
+        guard let parentStack = context.parentStack else {
+
+            CoreStore.log(
+                .warning,
+                message: "Attempted to perform a fetch but the \(cs_typeName(DataStack.self)) has already been deallocated."
+            )
+            throw CoreStoreError.unknown
+        }
+        fetchRequest.entity = parentStack.entityDescription(for: EntityIdentifier(self.entityClass))!
         guard applyAffectedStores else {
             
             return

Sources/ListMonitor.swift

@@ -963,8 +963,15 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
                     
                     return
                 }
-                
-                try! newFetchedResultsController.performFetchFromSpecifiedStores()
+                do {
+
+                    try newFetchedResultsController.performFetchFromSpecifiedStores()
+                }
+                catch {
+
+                    // DataStack may have been deallocated
+                    return
+                }
                 self.fetchedResultsControllerDelegate.taskGroup.notify(queue: .main) {
                     
                     self.fetchedResultsControllerDelegate.enabled = false