Fix IndexOutOfBoundsException when using empty BATCH statements

patch by Vovodroid; reviewed by Benjamin Lerer for CASSANDRA-10277

src/java/org/apache/cassandra/cql3/statements/BatchStatement.java

@@ -510,7 +510,7 @@ public class BatchStatement implements CQLStatement
 
             // Use the CFMetadata of the first statement for partition key bind indexes.  If the statements affect
             // multiple tables, we won't send partition key bind indexes.
-            Short[] partitionKeyBindIndexes = haveMultipleCFs ? null
+            Short[] partitionKeyBindIndexes = (haveMultipleCFs || batchStatement.statements.isEmpty())? null
                                                               : boundNames.getPartitionKeyBindIndexes(batchStatement.statements.get(0).cfm);
 
             return new ParsedStatement.Prepared(batchStatement, boundNames, partitionKeyBindIndexes);

test/unit/org/apache/cassandra/cql3/validation/operations/BatchTest.java

@@ -103,4 +103,10 @@ public class BatchTest extends CQLTester
                    row(111, "batchtext", null)
         );
     }
+
+    @Test
+    public void testBatchEmpty() throws Throwable
+    {
+        execute("BEGIN BATCH APPLY BATCH;");
+    }
 }