Error when uploading multiple images

If I remove the [url] attribute for the component and I try to upload multiple images I get this error:

ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'size' of undefined
TypeError: Cannot read property 'size' of undefined
    at image-upload.component.js:152
    at step (image-upload.component.js:32)
    at Object.next (image-upload.component.js:13)
    at step (image-upload.component.js:17)
    at Object.next (image-upload.component.js:13)
    at fulfilled (image-upload.component.js:4)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:388)
    at Object.onInvoke (core.js:3820)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:387)
    at Zone.push../node_modules/zone.js/dist/zone.js.Zone.run (zone.js:138)
    at image-upload.component.js:152
    at step (image-upload.component.js:32)
    at Object.next (image-upload.component.js:13)
    at step (image-upload.component.js:17)
    at Object.next (image-upload.component.js:13)
    at fulfilled (image-upload.component.js:4)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:388)
    at Object.onInvoke (core.js:3820)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:387)
    at Zone.push../node_modules/zone.js/dist/zone.js.Zone.run (zone.js:138)
    at resolvePromise (zone.js:814)
    at zone.js:724
    at fulfilled (image-upload.component.js:4)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:388)
    at Object.onInvoke (core.js:3820)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (zone.js:387)
    at Zone.push../node_modules/zone.js/dist/zone.js.Zone.run (zone.js:138)
    at zone.js:872
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:421)
    at Object.onInvokeTask (core.js:3811)

I can't share any code for this project, just thought I might let you guys know.