Bug 94367 cannot clear compiler compliance setting at the project level
i200505092010 Cannot disable the Java compiler project-specific preferences for some projects. Steps to reproduce: 1 - check out from CVS a Java project that has project-specific Java compiler settings enabled (example: org.eclipse.core.runtime). 2 - open the properties dialog for the project, select the Java compiler node, disable project-specific Java compiler preferences. 3 - Commit the changes by pressing "Ok" and reopen the properties dialog. It looks like the settings were not saved (project-specific settings are still enabled).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/OptionsConfigurationBlock.java
public String getStoredValue(IScopeContext[] lookupOrder, boolean ignoreTopScope, IWorkingCopyManager manager) {
			for (int i= ignoreTopScope ? 1 : 0; i < lookupOrder.length; i++) {
				String value= getStoredValue(lookupOrder[i], manager);
				if (value != null) {
					return value;
				}
			}
			return null;
		}
		
		public void setStoredValue(IScopeContext context, String value, IWorkingCopyManager manager) {
			if (value != null) {
				getNode(context, manager).put(fKey, value);
			} else {
				getNode(context, manager).remove(fKey);
			}
		}
			
		/* (non-Javadoc)
		 * @see java.lang.Object#toString()
		 */
		public String toString() {
			return fQualifier + '/' + fKey;
		}
		public String getQualifier() {
			return fQualifier;
		}
	}
	
	protected static class ControlData {