Incorrect condition check in getEntry(long index).

[liang636600]

Hi, @wenweihu86 , I think there is an issue with the condition that directly returns null when endIndex == 0. This is because there is a type of Segment file named open-i, which typically indicates that the Segment can continue accepting new entries, and their endIndex is represented as 0. If such a condition is set, when the function's input index falls within a Segment like open-i, it will only return null, which I think is inappropriate.

raft-java/raft-java-core/src/main/java/com/github/wenweihu86/raft/storage/Segment.java

Lines 31 to 34 in 50761c6

	public RaftProto.LogEntry getEntry(long index) {
	if (startIndex == 0 || endIndex == 0) {
	return null;
	}

Suggested fix: if (startIndex == 0 || endIndex == 0) => if (startIndex == 0)

I'm looking forward to your confirmation, and would be happy to help fix the issue if needed.