Port JBIDE-7340 to JBDS:

With the JSF Facet included, a web.xml containing a location

<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>/error</location>
</error-page>

is indicated as an error with the message "Attribute location references to /error that does note exist in web content." even though the web.xml does contain the mapping:

<servlet-mapping>
<servlet-name>Error Servlet</servlet-name>
<url-pattern>/error</url-pattern>
</servlet-mapping>