background image heading errors

hello, when i try to change a category image i get a bunch of warnings related to those lines of code in this file: ax-meta-class.php :

Illegal string offset ‘url’ line 721 :
Cannot assign an empty string to a string offset line 721:
Illegal string offset ‘id’ line 723
Cannot assign an empty string to a string offset 723:
Illegal string offset ‘url’ line 724:
Cannot assign an empty string to a string offset line 724
Cannot assign an empty string to a string offset line 724
Illegal string offset ‘url’ line 733
llegal string offset ‘id’ line 734
Illegal string offset ‘url’ line 735

719`//backwords capability
if ( !isset( $value[‘url’] ) )
$value[‘url’] = ”;
if ( !isset( $value[‘id’] ) )
$value[‘id’] = ”;
$value[‘url’] = isset( $value[‘src’] ) ? $value[‘src’] : $value[‘url’];
$has_image = empty( $value[‘url’] ) ? false : true;
$w = isset( $field[‘width’] ) ? $field[‘width’] :
‘auto’;
$h = isset( $field[‘height’] ) ? $field[‘height’] : ‘auto’;
$PreviewStyle = “style=’width: $w; height: $h;” . ( ( !$has_image ) ? “display: none;'” : “‘” );
$id = $field[‘id’];
$multiple = isset( $field[‘multiple’] ) ? $field[‘multiple’] : false;
$multiple = ( $multiple ) ? “multiFile ” : “”;

echo “<span class=’simplePanelImagePreview’><img {$PreviewStyle} src='{$value[‘url’]}’><br/></span>”;
echo “<input type=’hidden’ name='{$name}[id]’ value='{$value[‘id’]}’/>”;
echo “<input type=’hidden’ name='{$name}[url]’ value='{$value[‘url’]}’/>”;
if ( $has_image )
echo “<input class='{$multiple} button simplePanelimageUploadclear’ id='{$id}’ value='” . __( ‘Remove Image’ ) . “‘ type=’button’/>”;
else
echo “<input class='{$multiple} button simplePanelimageUpload’ id='{$id}’ value='” . __( ‘Upload Image’ ) . “‘ type=’button’/>”;
$this->show_field_end( $field, $meta );
}//741
`