[test] SmartImportTests fix NPE after SWTError: No more handles

[jukzi]

No description provided.

[jukzi]

was:

java.lang.NullPointerException: Cannot invoke "org.eclipse.swt.widgets.Shell.isDisposed()" because the return value of "org.eclipse.jface.wizard.WizardDialog.getShell()" is null
at org.eclipse.ui.tests.datatransfer.SmartImportTests.proceedSmartImportWizard(SmartImportTests.java:160)
at org.eclipse.ui.tests.datatransfer.SmartImportTests.testConfigurationCloseImportedProjects(SmartImportTests.java:292)
at java.base/java.lang.reflect.Method.invoke(Method.java:569)

https://download.eclipse.org/eclipse/downloads/drops4/I20241027-1800/testresults/html/org.eclipse.ui.tests_ep434I-unit-win32-java17_win32.win32.x86_64_17.html

[github-actions]

Test Results

 1 821 files  ±0   1 821 suites  ±0   1h 53m 47s ⏱️ + 6m 0s
 7 714 tests ±0   7 486 ✅ ±0  228 💤 ±0  0 ❌ ±0 
24 303 runs  ±0  23 556 ✅ ±0  747 💤 ±0  0 ❌ ±0 

Results for commit 666bad5. ± Comparison against base commit ec2d9bd.