description:
exception is thrown out when press enter for font color value list in "new style" dialogue.

build number:
2.6.0.v20100331-0630

steps to reproduce:
1. new a style.
2. go to "font" tab, click the color list and input "re" and press enter.
3. click the color list and input "red" and press enter.

expected result:
no exception.

actual result:
exception is thrown out.
error log:
org.eclipse.swt.swtexception: failed to execute runnable (java.lang.nullpointerexception)
at org.eclipse.swt.swt.error(swt.java:4083)
at org.eclipse.swt.swt.error(swt.java:3998)
at org.eclipse.swt.widgets.synchronizer.runasyncmessages(synchronizer.java:137)
at org.eclipse.swt.widgets.display.runasyncmessages(display.java:4012)
at org.eclipse.swt.widgets.display.readanddispatch(display.java:3631)
at org.eclipse.ui.internal.workbench.runeventloop(workbench.java:2416)
at org.eclipse.ui.internal.workbench.runui(workbench.java:2380)
at org.eclipse.ui.internal.workbench.access$4(workbench.java:2229)
at org.eclipse.ui.internal.workbench$5.run(workbench.java:504)
at org.eclipse.core.databinding.observable.realm.runwithdefault(realm.java:332)
at org.eclipse.ui.internal.workbench.createandrunworkbench(workbench.java:497)
at org.eclipse.ui.platformui.createandrunworkbench(platformui.java:149)
at org.eclipse.ui.internal.ide.application.ideapplication.start(ideapplication.java:115)
at org.eclipse.equinox.internal.app.eclipseapphandle.run(eclipseapphandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.eclipseapplauncher.runapplication(eclipseapplauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.eclipseapplauncher.start(eclipseapplauncher.java:79)
at org.eclipse.core.runtime.adaptor.eclipsestarter.run(eclipsestarter.java:369)
at org.eclipse.core.runtime.adaptor.eclipsestarter.run(eclipsestarter.java:179)
at sun.reflect.nativemethodaccessorimpl.invoke0(native method)
at sun.reflect.nativemethodaccessorimpl.invoke(nativemethodaccessorimpl.java:39)
at sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodaccessorimpl.java:25)
at java.lang.reflect.method.invoke(method.java:597)
at org.eclipse.equinox.launcher.main.invokeframework(main.java:619)
at org.eclipse.equinox.launcher.main.basicrun(main.java:574)
at org.eclipse.equinox.launcher.main.run(main.java:1406)
caused by: java.lang.nullpointerexception
at org.eclipse.birt.report.designer.internal.ui.dialogs.abstractfieldeditor$1.run(abstractfieldeditor.java:251)
at org.eclipse.swt.widgets.runnablelock.run(runnablelock.java:35)
at org.eclipse.swt.widgets.synchronizer.runasyncmessages(synchronizer.java:134)
... 22 more
fixed it.

check the null point logic.
verified in build (2.6.0.v20100428-0630), closed.