dcache-xroot: check that descriptor is not null before calling close …

…-- fix

73e683a
https://rb.dcache.org/r/14180/

still risks an NPE.  This fixes it.

Acked-by: Tigran
Acked-by: Lea

modules/dcache-xrootd/src/main/java/org/dcache/xrootd/pool/XrootdPoolRequestHandler.java

@@ -18,7 +18,6 @@
 package org.dcache.xrootd.pool;
 
 import static java.nio.charset.StandardCharsets.US_ASCII;
-import static java.util.function.Predicate.not;
 import static org.dcache.xrootd.protocol.XrootdProtocol.UUID_PREFIX;
 import static org.dcache.xrootd.protocol.XrootdProtocol.kXR_ArgInvalid;
 import static org.dcache.xrootd.protocol.XrootdProtocol.kXR_ArgMissing;
@@ -52,6 +51,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
@@ -946,7 +946,7 @@ private FileDescriptor getDescriptorAtomically(int fd) throws XrootdException {
 
     @GuardedBy("writeLock")
     private void removeAllDescriptorsAtomically() {
-        _descriptors.stream().filter(not(null)).forEach(FileDescriptor::close);
+        _descriptors.stream().filter(Objects::nonNull).forEach(FileDescriptor::close);
         _descriptors.clear();
     }