An incomplete fix for the NPE bugs in WebappStructure.java

The fix revision 712569 was aimed to remove an NPE bug on the value of "dependenciesInfo " in the method "getDependencies" of the file "/maven/plugins/trunk/maven-war-plugin/src/main/java/org/apache/maven/plugin/war/util/WebappStructure.java" , but it is incomplete.
Since the value "dependenciesInfo " could be null during the runtime execution, its value should also be null-checked before being dereferenced in other methods.

The buggy code locations the same fix needs to be applied at are as bellows:

Line 389 of the method "registerTargetFileName";

public void registerTargetFileName( Artifact artifact, String targetFileName )
    {
[Line 389] final Iterator it = dependenciesInfo.iterator();
        while ( it.hasNext() )
        {
            DependencyInfo dependencyInfo = (DependencyInfo) it.next();
            if ( WarUtils.isRelated( artifact, dependencyInfo.getDependency() ) )
            {
                dependencyInfo.setTargetFileName( targetFileName );
            }
        }
    }