False positive on jpgs in gallery

Hi.
Thanks for the great plugin.

I use it in an installation with various other shorttags and plugins.
I noticed thata for jps’s in a gallery it gave false positive and replaces the src of jpgs with the <object .. template.
In order to solve this I added the following check about the extention of the $src in vpdfe_pdf_embed_html() function.

function vpdfe_pdf_embed_html( $src , $title = '' , $w = '100%' , $h = '500em' ) {
    // if $content is a URL pointing to an attachment page on this WordPress
    // site then get the PDF's actual URL

    if ( $id = vpdfe_extract_id_from_wp_url( $src ) ) {
        $wp_post = get_post( $id ) ;
        if ( $wp_post->post_type != 'attachment' || $wp_post->post_mime_type != 'application/pdf' ) {
            return ;
        }
        $src = wp_get_attachment_url( $wp_post->ID ) ;

        if ( ! isset( $title ) ) {
            $title = $wp_post->post_title ;
        }
    }
//Check if it is really a pdf
    if ( substr( $src , '-3' ) != 'pdf' ) {
        return ;
    }
    // FitH will fit the page width in the embed window
    $template = '<object class="vanilla-pdf-embed" data="%1$s#page=1&view=FitH" type="application/pdf" %3$s %4$s>
    <p><a href="%1$s">Download the PDF file%2$s.</a></p>
</object>' ;

    return sprintf( $template , esc_url( $src ) , esc_attr( " $title" ) , ($w ? 'width="' . esc_attr( $w ) . '"' : '' ) , ($h ? 'height="' . esc_attr( $h ) . '"' : '' )
            ) ;
}

Do you think it will create other problems?

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