INSERT into SQLite database won't work in Swift

I'm calling a method for inserting data for task in table TASK in SQLite file. When I copy generated query to SQLite Free tool or some other tool query works fine and the record is inserted. But in XCode I get output in console:

Record(s) inserted...
fatal error: unexpectedly found nil while unwrapping an Optional value

and application crashes.

The code is below:

    func saveDataToDatabase(dataToSave: NSArray, requestedMethod: String) {
            let documents = try! NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false);
            let fileURL = documents.URLByAppendingPathComponent(DatabaseConstants.databaseName);
            var db: COpaquePointer = nil;
            if sqlite3_open(fileURL.path!, &db) == SQLITE_OK {
                print("Database opened...");
                if (dataToSave.count != 0) {
                    for (var i=0; i<dataToSave.count; i++) {
                        var query: String = "";
                        if (requestedMethod == ServiceMethodsConstants.getAllTasksForUserPluginResponse) {
                            query = "INSERT INTO TASK VALUES (null, '\(dataToSave[i].valueForKey("ACTION")!)', '\(dataToSave[i].valueForKey("ACTUAL_ENDING_DATE")!)', '\(dataToSave[i].valueForKey("ACTUAL_STARTING_DATE")!)', '\(dataToSave[i].valueForKey("ASSIGNOR")!)', \(dataToSave[i].valueForKey("ASSIGNOR_USER_ID")!), '\(dataToSave[i].valueForKey("CONTEXT_CLASS")!)', '\(dataToSave[i].valueForKey("CONTEXT_ID")!)', '\(dataToSave[i].valueForKey("CREATION_DATE")!)', '\(dataToSave[i].valueForKey("CREATOR")!)', '\(dataToSave[i].valueForKey("DESCRIPTION")!)', '\(dataToSave[i].valueForKey("ENDING_DATE")!)', '\(dataToSave[i].valueForKey("ESTIMATED_EFFORT")!)', \(dataToSave[i].valueForKey("ID")!), '\(dataToSave[i].valueForKey("NUMBER")!)', '\(dataToSave[i].valueForKey("PRIORITY")!)', '\(dataToSave[i].valueForKey("PROGRESS")!)', '\(dataToSave[i].valueForKey("PROJECT_NAME")!)', '\(dataToSave[i].valueForKey("STARTING_DATE")!)', '\(dataToSave[i].valueForKey("STATUS")!)', '\(dataToSave[i].valueForKey("TASK_NAME")!)', '\(dataToSave[i].valueForKey("TYPE")!)', 0)";
                          print(query);
                        } else if (requestedMethod == ServiceMethodsConstants.getAllProjectsMAResponse) {
                            query = "";
                        }
                        var statement: COpaquePointer = nil;
                        if sqlite3_prepare_v2(db, query, -1, &statement, nil) != SQLITE_OK {
                            let errmsg = String.fromCString(sqlite3_errmsg(db));
                            print("Error preparing insert: \(errmsg)");
                        }
                        if sqlite3_step(statement) != SQLITE_DONE {
                            let errmsg = String.fromCString(sqlite3_errmsg(db));
                            print("Failure inserting record(s): \(errmsg)");
                        } else {
                            print("Record(s) inserted...");
                            if sqlite3_reset(statement) != SQLITE_OK {
                                let errmsg = String.fromCString(sqlite3_errmsg(db))
                                print("Error resetting prepared statement: \(errmsg)")
                            }
                        }
                    }
                    if sqlite3_close(db) != SQLITE_OK {
                        print("Database closed...");
                    } else {
                        print("Error closing database");
                    }
                }
            } else {
                print("Error opening database...");
            }
        }

Can someone please help me fix this? Thanks for your help.