MINOR: ignore null judgement in LogCleaner (#19524)

about https://github.com/apache/kafka/pull/19387/files#r2052025917

Reviewers: PoAn Yang <[email protected]>, Chia-Ping Tsai
 <[email protected]>, TengYao Chi <[email protected]>

Author: gongxuanzhang

Diff for: storage/src/main/java/org/apache/kafka/storage/internals/log/LogCleaner.java

@@ -556,15 +556,14 @@ private boolean cleanFilthiestLog() throws LogCleaningException {
             } else {
                 // there's a log, clean it
                 this.lastPreCleanStats = preCleanStats;
-                LogToClean cleanable = null;
+                LogToClean cleanable = ltc.get();
                 try {
-                    cleanable = ltc.get();
                     cleanLog(cleanable);
                     cleaned = true;
                 } catch (ThreadShutdownException e) {
                     throw e;
                 } catch (Exception e) {
-                    throw new LogCleaningException(cleanable != null ? cleanable.log() : null, e.getMessage(), e);
+                    throw new LogCleaningException(cleanable.log(), e.getMessage(), e);
                 }
             }