[Fix][Connector-V2] Fix paimon e2e error (#7721)

Author: hawk9821

seatunnel-connectors-v2/connector-paimon/src/main/java/org/apache/seatunnel/connectors/seatunnel/paimon/sink/PaimonSinkWriter.java

@@ -83,7 +83,7 @@ public class PaimonSinkWriter
 
     private final TableSchema tableSchema;
 
-    private final PaimonBucketAssigner bucketAssigner;
+    private PaimonBucketAssigner bucketAssigner;
 
     private final boolean dynamicBucket;
 
@@ -103,14 +103,16 @@ public PaimonSinkWriter(
         this.context = context;
         this.jobContext = jobContext;
         this.tableSchema = ((FileStoreTable) table).schema();
-        this.bucketAssigner =
-                new PaimonBucketAssigner(
-                        table,
-                        this.context.getNumberOfParallelSubtasks(),
-                        this.context.getIndexOfSubtask());
         BucketMode bucketMode = ((FileStoreTable) table).bucketMode();
         this.dynamicBucket =
                 BucketMode.DYNAMIC == bucketMode || BucketMode.GLOBAL_DYNAMIC == bucketMode;
+        if (dynamicBucket) {
+            this.bucketAssigner =
+                    new PaimonBucketAssigner(
+                            table,
+                            this.context.getNumberOfParallelSubtasks(),
+                            this.context.getIndexOfSubtask());
+        }
         PaimonSecurityContext.shouldEnableKerberos(paimonHadoopConfiguration);
     }