[OCISDEV-492] Space image not uploaded if larger than 7MB

## Describe the bug

`Edit image` does not work if the image is larger that 7MB

## Steps to reproduce
1. Select `Edit image` on a space with `manager` permission
2. Choose an image larger that 7MB

## Expected behavior

Two options:

- Image updated correctly
- Error message: `image is larger than allowed` or similar, returning a proper error to the clients

## Actual behavior

Image not updated, but success message

## Setup

ownCloud Infinite Scale
Edition Community
Version 7.3.0
Web client version 12.1.1