Remove error on starting batch accessibility map

We had this error when we started a new batch accessiblity map calculation:
TypeError: Cannot read properties of undefined (reading 'errors')

Change is to use optional chaining and provides an empty array as fallback for errors and warnings
which might not be yet present in the routingResult when we just create the job.

Author: greenscientist

packages/transition-frontend/src/components/forms/accessibilityMap/AccessibilityMapBatchForm.tsx

@@ -173,8 +173,8 @@ class AccessibilityMapBatchForm extends ChangeEventsForm<
             const routingResult: any = await BatchAccessibilityMapCalculator.calculate(this.state.object);
             this.setState({
                 batchRoutingInProgress: false,
-                errors: routingResult.errors,
-                warnings: routingResult.warnings
+                errors: routingResult?.errors ?? [],
+                warnings: routingResult?.warnings ?? []
             });
         } catch (error) {
             this.setState({