bug: CodedInputStream.newInstance(List) with an empty bytebuffer produces an error

What version of protobuf and what language are you using? Language: Java: originally found in 3.25.4, still present in 4.33.0-RC2

What operating system (Linux, Windows, ...) and version? Tested MacOS 15.6.1, Linux 5.14.0

What runtime / compiler are you using (e.g., python version or gcc version) N/A

What did you do? Steps to reproduce the behavior:

1. Create a CodedInputStream with an empty list
2. Confirm that readTag() returns 0
3. Create a CodedInputStream with a single empty ByteBuffer
4. Call readTag()

import com.google.protobuf.CodedInputStream
import java.nio.ByteBuffer
import java.util.List

public class App {
  public static void main(String[] args) {
    CodedInputStream cis = CodedInputStream.newInstance(List.of())
    System.out.println(cis.readTag());//success, returns 0

    cis = CodedInputStream.newInstance(List.of(ByteBuffer.wrap(new byte[0])));
    System.out.println(cis.readTag());//failure, throws exception
  }
}

What did you expect to see Should return zero, same as readTag() for an empty list

What did you see instead?

Exception java.lang.IllegalStateException: class com.google.protobuf.IterableByteBufferInputStream#read(byte[]) returned invalid result: 0
The InputStream implementation is buggy.
      at CodedInputStream$StreamDecoder.tryRefillBuffer (CodedInputStream.java:2882)
      at CodedInputStream$StreamDecoder.isAtEnd (CodedInputStream.java:2794)
      at CodedInputStream$StreamDecoder.readTag (CodedInputStream.java:2151)

Note that empty ByteBuffers within a larger collection do not seem to cause a problem with some quick testing, just a collection with only empty ByteBuffers in it.

CodedInputStream cis = CodedInputStream.newInstance(List.of(ByteBuffer.allocate(0), ByteBuffer.wrap(new byte[]{0x0a}), ByteBuffer.wrap(new byte[]{0x01, 0x61})))
System.out.println(cis.readTag());// success
System.out.println(cis.readString());