Fix JsonObjectDecoder with '[' starting chunk

Issue: SPR-15013

spring-web/src/main/java/org/springframework/http/codec/json/JsonObjectDecoder.java

@@ -212,9 +212,6 @@ class JsonObjectDecoder extends AbstractDecoder<DataBuffer> {
 					}
 				}
 
-				if (this.input.readableBytes() == 0) {
-					this.index = 0;
-				}
 				return Flux.fromIterable(chunks);
 			}
 

spring-web/src/test/java/org/springframework/http/codec/json/JsonObjectDecoderTests.java

@@ -106,6 +106,19 @@ public class JsonObjectDecoderTests extends AbstractDataBufferAllocatingTestCase
 				.expectNext("{\"foo\": \"baz\"}")
 				.expectComplete()
 				.verify();
+
+		// SPR-15013
+		source = Flux.just(stringBuffer("["), stringBuffer("{\"id\":1,\"name\":\"Robert\"}"),
+						stringBuffer(","), stringBuffer("{\"id\":2,\"name\":\"Raide\"}"),
+						stringBuffer(","), stringBuffer("{\"id\":3,\"name\":\"Ford\"}"),
+						stringBuffer("]"));
+		output = decoder.decode(source, null, null, Collections.emptyMap()).map(JsonObjectDecoderTests::toString);
+		StepVerifier.create(output)
+				.expectNext("{\"id\":1,\"name\":\"Robert\"}")
+				.expectNext("{\"id\":2,\"name\":\"Raide\"}")
+				.expectNext("{\"id\":3,\"name\":\"Ford\"}")
+				.expectComplete()
+				.verify();
 	}