Check cluster serviceable before get GetSegmentInfos for distribution (#22317)

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

internal/querynode/shard_cluster.go

@@ -863,7 +863,14 @@ func (sc *ShardCluster) Query(ctx context.Context, req *querypb.QueryRequest, wi
 }
 
 func (sc *ShardCluster) GetSegmentInfos() []SegmentEntry {
-	items, version := sc.distribution.GetCurrent()
+	sc.mutVersion.RLock()
+	distribution := sc.distribution
+	sc.mutVersion.RUnlock()
+	// before setup version
+	if distribution == nil {
+		return nil
+	}
+	items, version := distribution.GetCurrent()
 	sc.finishUsage(version)
 
 	var result []SegmentEntry

internal/querynode/shard_cluster_test.go

@@ -2128,3 +2128,15 @@ func (suite *ShardClusterSuite) TestReleaseSegments() {
 func TestShardClusterSuite(t *testing.T) {
 	suite.Run(t, new(ShardClusterSuite))
 }
+
+// ut for https://github.com/milvus-io/milvus/issues/22312
+func TestGetSegmentInfoBeforeSetup(t *testing.T) {
+
+	sc := NewShardCluster(100, 1000, "testChannel", 0,
+		&mockNodeDetector{}, &mockSegmentDetector{}, buildMockQueryNode)
+
+	assert.NotPanics(t, func() {
+		result := sc.GetSegmentInfos()
+		assert.Nil(t, result)
+	})
+}