JAVA_HOME issue in web3signer

[oxptaube]

Describe the bug
web3singer package does not start, with the following Log entries:

Setting up watches. Beware: since -r was given, this may take a while!
Watches established.
Setting up watches.
Watches established.

ERROR: JAVA_HOME is set to an invalid directory: /opt/java/openjdk

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation.

To Reproduce

1. Installed Core and Prysm to newest version see below
2. Installed web3signer by Dappstore successfully
3. Reset loop of web3signer with the error logs:

Setting up watches. Beware: since -r was given, this may take a while!
Watches established.
Setting up watches.
Watches established.

ERROR: JAVA_HOME is set to an invalid directory: /opt/java/openjdk

Expected behavior

Web3signer should start

DAppNode version:

Core DAppNode Packages versions
bind.dnp.dappnode.eth: 0.2.6
core.dnp.dappnode.eth: 0.2.57
dappmanager.dnp.dappnode.eth: 0.2.45, commit: 7b9ad9ad
https.dnp.dappnode.eth: 0.1.3
ipfs.dnp.dappnode.eth: 0.2.15
vpn.dnp.dappnode.eth: 0.2.8, commit: f9a8743e
wifi.dnp.dappnode.eth: 0.2.8
wireguard.dnp.dappnode.eth: 0.1.1
System info
dockerComposeVersion: 1.25.5
dockerServerVersion: 19.03.8
dockerCliVersion: 19.03.8
os: debian
versionCodename: buster
architecture: amd64
kernel: 4.19.0-21-amd64
Disk usage: 32%