DefaultModuleService: fix bug in conditional order

This makes 1e046ce work as intended...
almost. There is still a problem with the PrefService's remove method,
which will be fixed in the subsequent series of commits.

Author: ctrueden

src/main/java/org/scijava/module/DefaultModuleService.java

@@ -521,6 +521,6 @@ private Class<?> prefClass(final ModuleItem<?> item) {
 	private String prefKey(final ModuleItem<?> item) {
 		final String persistKey = item.getPersistKey();
 		return persistKey == null || persistKey.isEmpty() ? //
-			persistKey : item.getName();
+			item.getName() : persistKey;
 	}
 }