better error checks for failure conditions (based on Puneet Pawaia's reports)

lib/ftp.c

@@ -1720,12 +1720,14 @@ CURLcode Curl_ftp_disconnect(struct connectdata *conn)
 {
   struct FTP *ftp= conn->proto.ftp;
 
-  if(ftp->user)
-    free(ftp->user);
-  if(ftp->passwd)
-    free(ftp->passwd);
-  if(ftp->entrypath)
-    free(ftp->entrypath);
-
+  /* The FTP session may or may not have been allocated/setup at this point! */
+  if(ftp) {
+    if(ftp->user)
+      free(ftp->user);
+    if(ftp->passwd)
+      free(ftp->passwd);
+    if(ftp->entrypath)
+      free(ftp->entrypath);
+  }
   return CURLE_OK;
 }