Catch NoClassDefFoundError while locating sources

If the locator is unable to locate some sources due to a classlaoding
problem this currently leads to an ugly exception window showing up.

This now adds NoClassDefFoundError to the catch clause to prevent annoy
the user in such case.

Author: laeubi

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/SourceLocationManager.java

@@ -323,7 +323,7 @@ private IPath searchExtensionLocations(IPath relativePath, IPluginBase plugin) {
 		return getExtensions().locators.stream().map(locator -> {
 			try {
 				return locator.locator.locateSource(plugin);
-			} catch (RuntimeException e) {
+			} catch (RuntimeException | NoClassDefFoundError e) {
 				return null;
 			}
 		}).filter(Objects::nonNull).findFirst().orElse(null);