Android Firebase changing user email address error -

when trying let user change his/her email address firebase gives error. not error invalid email or password, default error message (the third toast message "an error occured"). in logcat of application no errors. says "success". source error in firebase?

mfirebaseref = new firebase(constants.firebase_url);                     mfirebaseref.changeemail(email, mail, password, new firebase.resulthandler() {                         @override                         public void onsuccess() {                             toast.maketext(getactivity(), "email address changed!", toast.length_long).show();                          }                          @override                         public void onerror(firebaseerror firebaseerror) {                             // error encountered                             switch (firebaseerror.getcode()) {                                 case firebaseerror.user_does_not_exist:                                     toast.maketext(getactivity(), "unknown user", toast.length_long).show();                                     break;                                 case firebaseerror.invalid_password:                                     toast.maketext(getactivity(), "invalid password", toast.length_long).show();                                     break;                                 default:                                     toast.maketext(getactivity(), "an error occured", toast.length_long).show();                                     break;                             }                         }                     });