Bug 796579 - Cannot go forward with empty duplicates screen

Set the key name to (default-unspec-acct) for the case where both payee
and memo are blank so that it can be found, then
look for that key in the right hash, qif-memo-map, instead of looking for
cat (already known to be "") in the wrong hash, qif-cat-map.

gnucash/import-export/qif-imp/qif-dialog-utils.scm

@@ -586,6 +586,8 @@
                                (begin
                                  (set! entry (make-qif-map-entry))
                                  (qif-map-entry:set-qif-name! entry key-string)
+                                 (if (string=? key-string "")
+                                     (set! key-string (default-unspec-acct)))
                                  (qif-map-entry:set-gnc-name!
                                   entry (default-unspec-acct))
                                  (qif-map-entry:set-allowed-types!

gnucash/import-export/qif-imp/qif-to-gnc.scm

@@ -587,7 +587,9 @@
                                     (not (string=? memo ""))
                                     (hash-ref qif-memo-map memo))))
                      (if (not far-acct-info)
-                         (set! far-acct-info (hash-ref qif-cat-map cat)))))
+                                (set! far-acct-info
+                                      (hash-ref qif-memo-map
+                                                (default-unspec-acct))))))
 
                    (set! far-acct-name (qif-map-entry:gnc-name far-acct-info))
                    (set! far-acct (hash-ref gnc-acct-hash far-acct-name))