Explicitly set labels to nil for Alert Policy

Signed-off-by: Modular Magician <[email protected]>

google/resource_monitoring_alert_policy.go

@@ -827,6 +827,18 @@ func resourceMonitoringAlertPolicyRead(d *schema.ResourceData, meta interface{})
 		return handleNotFoundError(err, d, fmt.Sprintf("MonitoringAlertPolicy %q", d.Id()))
 	}
 
+	res, err = resourceMonitoringAlertPolicyDecoder(d, meta, res)
+	if err != nil {
+		return err
+	}
+
+	if res == nil {
+		// Decoding the object has resulted in it being gone. It may be marked deleted
+		log.Printf("[DEBUG] Removing MonitoringAlertPolicy because it no longer exists.")
+		d.SetId("")
+		return nil
+	}
+
 	if err := d.Set("project", project); err != nil {
 		return fmt.Errorf("Error reading AlertPolicy: %s", err)
 	}
@@ -1849,3 +1861,10 @@ func expandMonitoringAlertPolicyDocumentationContent(v interface{}, d TerraformR
 func expandMonitoringAlertPolicyDocumentationMimeType(v interface{}, d TerraformResourceData, config *Config) (interface{}, error) {
 	return v, nil
 }
+
+func resourceMonitoringAlertPolicyDecoder(d *schema.ResourceData, meta interface{}, res map[string]interface{}) (map[string]interface{}, error) {
+	if err := d.Set("labels", nil); err != nil {
+		return res, fmt.Errorf("Error ignoring Removed fields for AlertPolicy: %s", err)
+	}
+	return res, nil
+}