In MATLAB 2019a on Linux based OS, trying to access the System Generator for DSP or Model Composer documentation or demo examples results in a "java exception" error, or a page which is rendered badly.
This is a known issue for the Vivado System Generator for DSP and Model Composer.
If you encounter these issues, it is recommended to contact MathWorks support for further assistance.
The issues have only been observed on Linux platforms.
As a work-around, Windows OS based machines can be used.