Fixed a fragility in which drscheme might fail to start up

if no planet packages are installed

svn: r3542

collects/planet/cachepath.ss

@@ -5,7 +5,10 @@
 
   ;; get-planet-cache-path : -> path[absolute, file]
   ;; the path to the cache.ss file for the planet installation
-  ;; SIDE EFFECT: creates the directory if it doesn't already exist
+  ;; (n.b. this used to have the side effect of creating the path
+  ;; if it didn't exist, but since this function may be run at
+  ;; setup time and setup-time programs must not create this sort 
+  ;; of directory, it doesn't do that anymore)
   (define (get-planet-cache-path)
     (let ((path (build-path (PLANET-DIR) "cache.ss")))
       path)))

collects/setup/getinfo.ss

@@ -113,11 +113,13 @@
 				   i
 				   f)]))
 		       (let ([l (with-input-from-file f read)])
-			 (unless (list? l)
-			   (error 'find-relevant-directories
-				  "bad info-domain cache file: ~a" 
-				  f))
-			 l)))))
+			 (cond
+                           [(list? l) l]
+                           [(eof-object? l) '()] ;; allow completely empty files
+                           [else
+                            (error 'find-relevant-directories
+                                   "bad info-domain cache file: ~a" 
+                                   f)]))))))
 		(reverse (table-paths t)))
       ;; For each coll, invert the mapping, adding the col name to the list for each sym: 
       (hash-table-for-each colls