Unable to update installed libraries in Library Manager

Arduino IDE 1.9.0-beta build 170
Windows 10 64 bit / Ubuntu 19.04

1. Tools > Manage Libraries...
2. Select an installed library that has other releases available.
3. From the "Select version" dropdown menu, select any version.
4. Click the "Install" button.

The process fails with the error:
```
An error occurred while installing library!
java.lang.RuntimeException: java.lang.Exception: An error occurred while installing library!
at cc.arduino.contributions.libraries.ui.LibraryManagerUI.lambda$onInstallPressed$3(LibraryManagerUI.java:224)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.Exception: An error occurred while installing library!
at cc.arduino.contributions.libraries.LibraryInstaller.install(LibraryInstaller.java:94)
at cc.arduino.contributions.libraries.ui.LibraryManagerUI.lambda$onInstallPressed$3(LibraryManagerUI.java:216)
... 1 more
```
The same error occurs after clicking the "Update" button.

There is no problem when clicking the "Install" button of a library that is not already installed.

The issue does not occur with Arduino IDE 1.8.10 Hourly Build 2019/05/21 09:33.

Start in LibraryManagerUI.java at the install and update handlers shown in the stack trace, then follow the call into LibraryInstaller.java. Reproduce the failure with an already-installed library and compare it with installing a library for the first time; done means selecting another version or Update succeeds without regressing new-library installation.

Written by the indexing model from the issue text.