set base-dir more sensitively

quad/quadwriter/render.rkt

@@ -335,13 +335,16 @@
   ;; and looking for fonts and other assets.
 
   (match-define-values (base-dir _ _) (split-path
-                                       (match base-dir-arg
-                                         [#false (current-directory)]
+                                       (cond
                                          ;; for reasons unclear, DrRacket sometimes sneaks
                                          ;; an "unsaved editor" into this arg, despite efforts to prevent
                                          ;; probably my fault
-                                         ["unsaved editor" pdf-path-arg]
-                                         [path path])))
+                                         [(equal? base-dir-arg "unsaved editor") pdf-path-arg]
+                                         [base-dir-arg]
+                                         [pdf-path-arg]
+                                         ;; pdf-path-arg is #false when we're returning bytes,
+                                         ;; but we still need some directory, so current-directory is last resort.
+                                         [else (current-directory)])))
   
   (unless (directory-exists? base-dir)
     (raise-argument-error 'render-pdf "existing directory" base-dir))