helm: Helm 3.0.0 beta 4 - can't upgrade charts (existing resource conflict)

Hi, Bitnami developer here. When trying to upgrade a chart to a newer version using helm v3 beta 4, it fails due to an existing resource conflict. This never happened neither with helm v2 nor with the previous beta versions of helm v3. It seems to be related with commit https://github.com/helm/helm/commit/36f3a4b326f1df1ad50cfa19c47808a7e42bd294.

I would like to know if this is a bug or the expected behaviour, and in that case try to understand why this is happening. This is happening to all our charts.

Steps to reproduce:

1. Add the stable repository

helm repo add stable https://kubernetes-charts.storage.googleapis.com

1. Grab and install an older version of a chart (e.g. dokuwiki)

helm fetch --untar --untardir . stable/dokuwiki --version 5.0.0
helm install doku ./dokuwiki --namespace dokuwiki

1. Try to upgrade to the latest version

helm upgrade doku stable/dokuwiki --namespace dokuwiki 
Error: UPGRADE FAILED: rendered manifests contain a new resource that already exists. Unable to continue with update: existing resource conflict: kind: Deployment, namespace: amoreno, name: doku-dokuwiki

Note that running the above command with helm v3 beta 3 instead works correctly.

Output of helm version:

version.BuildInfo{Version:"v3.0.0-beta.4", GitCommit:"7ffc879f137bd3a69eea53349b01f05e3d1d2385", GitTreeState:"dirty", GoVersion:"go1.13.1"}

Output of kubectl version:

Client Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.3", GitCommit:"5e53fd6bc17c0dec8434817e69b04a25d8ae0ff0", GitTreeState:"clean", BuildDate:"2019-06-06T01:44:30Z", GoVersion:"go1.12.5", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"14+", GitVersion:"v1.14.6-gke.2", GitCommit:"c9de33b5439df6e206d7ba646787c6ace92d737b", GitTreeState:"clean", BuildDate:"2019-09-06T18:30:33Z", GoVersion:"go1.12.9b4", Compiler:"gc", Platform:"linux/amd64"}

Cloud Provider/Platform (AKS, GKE, Minikube etc.): GKE