I encountered same issue: every time you get it, you have to allocate more space and run DBeaver itself first with additional flags -vmargs -Xmx*m. Replace * with 2048 or 4096.
It doesn’t look like DBeaver takes garbage out when closing the script, so I had to restart application many times to check right amount of memory needed.
@Timothy Jannace just pointed out that you also can edit dbeaver.ini. Example.