Test is unstable (e.g. failed in tonight's I-build
https://download.eclipse.org/eclipse/downloads/drops4/I20240421-1800/testresults/html/org.eclipse.jdt.text.tests_ep432I-unit-cen64-gtk3-java17_linux.gtk.x86_64_17.html
).
This change replaces silent fails with proper exception reporting.