bolt: [BUG] Content->getImage() method breaks for images with alt and no path

The function Content->getImage() takes the first field of type image and the returns either the image path if we have a file key or the whole thing if not (as fallback for bolt 1.5.0).

If a user now edits the alt title of an image but does not provide a image path, this check fails and returns the array [alt: „the alt“]. Since every part of bolt (including especially the twig template of the backend) assume it’s a string and not an array, this throws an exception, making some views of the backend unusable.

The method in question - ContentValuesTrait.php Line 503

        // Grab the first field of type 'image', and return that.
        foreach ($this->contenttype['fields'] as $key => $field) {
            if ($field['type'] == 'image') {
                // After v1.5.1 we store image data as an array
                if (is_array($this->values[$key]) && isset($this->values[$key]['file'])) {
                    return $this->values[$key]['file'];
                }

                return $this->values[$key];
            }
        }

Example of a breaking template with a “Array to String Conversion”: __base/listing.twig

    {% set thumb_title = __('Image') ~ ': ' ~ content.getImage %}

In my case a widget that uses the @bolt/_base/listing.twig block creating the thumbnails breaks, making the dashboard fail critically (Remember: we can’t catch exceptions in twig).

Proposed Fix - ContentValuesTrait.php Line 503

        // Grab the first field of type 'image', and return that.
        foreach ($this->contenttype['fields'] as $key => $field) {
            if ($field['type'] == 'image') {
                // After v1.5.1 we store image data as an array
                if (is_array($this->values[$key])) {
                    return isset($this->values[$key]['file']) ? $this->values[$key]['file'] : "";
                }

                return $this->values[$key];
            }
        }

Details

• Relevant Bolt Version: 3.0.12
• Install type: Composer install
• PHP version: 5.5
• Used web server: Apache
• For UX/UI issues: Chrome

Reproduction

• Create a content type with a field of type image with alt attribute
• Enter an alt value and save
• Use the $record->getImage() method somewhere and observe returned file path