ox-publish: Fix including files with a search option

* lisp/ox-publish.el (org-publish-cache-file-needs-publishing): Remove
  double quotes prior to pruning search options.

Reported-by: Joseph Carter Osborn <jcosborn@ucsc.edu>
<http://lists.gnu.org/r/emacs-orgmode/2018-01/msg00317.html>

lisp/ox-publish.el

@@ -1260,25 +1260,21 @@ the file including them will be republished as well."
 	    (with-current-buffer buf
 	      (goto-char (point-min))
 	      (while (re-search-forward "^[ \t]*#\\+INCLUDE:" nil t)
-		(let* ((element (org-element-at-point))
-		       (included-file
-			(and (eq (org-element-type element) 'keyword)
-			     (let ((value (org-element-property :value element)))
-			       (and value
-				    (string-match
-				     "\\`\\(\".+?\"\\|\\S-+\\)\\(?:\\s-+\\|$\\)"
-				     value)
-				    (let ((m (match-string 1 value)))
-				      (org-unbracket-string
-				       "\"" "\""
-				       ;; Ignore search suffix.
-				       (if (string-match "::.*?\"?\\'" m)
-					   (substring m 0 (match-beginning 0))
-					 m))))))))
-		  (when included-file
-		    (push (org-publish-cache-ctime-of-src
-			   (expand-file-name included-file))
-			  included-files-ctime)))))
+		(let ((element (org-element-at-point)))
+		  (when (eq 'keyword (org-element-type element))
+		    (let* ((value (org-element-property :value element))
+			   (filename
+			    (and (string-match "\\`\\(\".+?\"\\|\\S-+\\)" value)
+				 (let ((m (org-unbracket-string
+					   "\"" "\"" (match-string 1 value))))
+				   ;; Ignore search suffix.
+				   (if (string-match "::.*?\\'" m)
+				       (substring m 0 (match-beginning 0))
+				     m)))))
+		      (when filename
+			(push (org-publish-cache-ctime-of-src
+			       (expand-file-name filename))
+			      included-files-ctime)))))))
 	  (unless visiting (kill-buffer buf)))))
     (or (null pstamp)
 	(let ((ctime (org-publish-cache-ctime-of-src filename)))