NPE in ResourceReader when InputSource returns null on getURI (COCOON-1935). Due to Alexander Klimetschek. Also sat the system id to something better than null (the block uri). The value still isn't globaly valid (or necessarily unique).
cocoon/trunk/core/cocoon-blocks-fw/cocoon-blocks-fw-impl/src/main/java/org/apache/cocoon/blocks/components/BlockSource.java