Allow empty texts with segments

This commit allows segments in an empty text segment to account for
segments with only an image.

text/text_extras.go

@@ -11,7 +11,9 @@ func SolidColor(rgb uint32) uint32 {
 	return (rgb << 8) | 0xFF
 }
 
-// IsEmpty returns true if the given rich segment's content is empty.
+// IsEmpty returns true if the given rich segment's content is empty. Note that
+// a rich text is not necessarily empty if the content is empty, because there
+// may be images within the segments.
 func (r Rich) IsEmpty() bool {
-	return r.Content == ""
+	return r.Content == "" && len(r.Segments) == 0
 }