Don't insert nil faces in shr

* shr.el (shr-insert-table): Don't add nil faces, because that
will show up in *Messages* as "Invalid face reference: nil [32
times]".

lisp/net/shr.el

@@ -1754,17 +1754,18 @@ The preference is a float determined from `shr-prefer-media-type'."
 				 align)))
 	      (dolist (line lines)
 		(end-of-line)
-		(let ((start (point)))
-		  (insert
-		   line
-		   (propertize " "
-			       'display `(space :align-to (,pixel-align))
-			       'face (and (> (length line) 0)
-					  (shr-face-background
-					   (get-text-property
-					    (1- (length line)) 'face line)))
-			       'shr-table-indent shr-table-id)
-		   shr-table-vertical-line)
+		(let ((start (point))
+                      (background (and (> (length line) 0)
+                                       (shr-face-background
+                                        (get-text-property
+                                         (1- (length line)) 'face line))))
+                      (space (propertize
+                              " "
+                              'display `(space :align-to (,pixel-align))
+                              'shr-table-indent shr-table-id)))
+                  (when background
+                    (setq space (propertize space 'face background)))
+		  (insert line space shr-table-vertical-line)
 		  (shr-colorize-region
 		   start (1- (point)) (nth 5 column) (nth 6 column)))
 		(forward-line 1))