Fix transactions for objects fetched from the db (not created in this image)

src/cache.lisp

@@ -12,7 +12,9 b''
   (declare (ignore obj))
   (maybe-lock
     (let ((*ignore-transaction* t))
-      (do-cache (call-next-method)))))
+      (let ((obj (call-next-method)))
+        (setf (value-backup obj) nil)
+        (do-cache obj)))))
 
 (defmethod mito:insert-dao ((obj cached-dao))
   (maybe-lock

t/tests.lisp

@@ -77,4 +77,10 b''
     (with-transaction ()
       (setf (slot obj) 42)
       (rollback))
-    (false (slot-boundp obj 'slot) "Transaction rollback failed to unbind a slot")))
+    (false (slot-boundp obj 'slot) "Transaction rollback failed to unbind a slot")
+    (remhash (mito:object-id obj) (mito-transactions.dev::class-cache 'test-object)))
+  (let (obj)
+    (with-transaction ()
+      (setf obj (find-dao 'test-object))
+      (setf (slot obj) 2))
+    (is = 2 (slot obj))))