`paragraphRange` signature does not specify the returning type could be nullable, leading to unexpected crashes

We've seen some crashes in WooCommerce for iOS coming from our AztecEditor wrapper. This seems to come from the underlying usage of paragraphRange, since assumes that the attachment passed into the method is the string, force-unwrapping the first result of the attachments array:

    func paragraphRange(for attachment: NSTextAttachment) -> NSRange {
        // We assume the attachment IS in the string.  This method should not be called otherwise.
        let attachmentRange = ranges(forAttachment: attachment).first!
        
        return paragraphRange(for: attachmentRange)
    }

This leads to unexpected crashes when the method is not used as intended, since its signature does not specify that the result could be nil. Ideally we should change the returning type to NSRange?, or handle the existence of nil values internally.

Start in Aztec/Classes/Extensions/NSAttributedString+ParagraphRange.swift at paragraphRange(for: NSTextAttachment), especially the ranges(forAttachment:) call. Search its callers to understand how the return value is used, then verify the attachment-not-found path no longer causes an unexpected crash and that affected callers handle the result appropriately.