X_RF, M_RF don't output CIs

[siyunyang]

I downloaded the Version 0.0.2.1, and ran the code on your example data and my own data. Both got the following error:
xl_rf <- X_RF(feat = feature_train, tr = w_train, yobs = yobs_train)
xl_ci_rf <- CateCI(xl_rf, feature_test, B = 50)
Error in CateCI(xl_rf, feature_test, B = 50) :
one of the groups might be too small to
do valid inference.

Same error was found for M_RF.

[v-rodriguez]

I have the same issue with T_RF