chore: fix potential nil pointer errors (#3454)

core/iox/bufferpool.go

@@ -32,6 +32,10 @@ func (bp *BufferPool) Get() *bytes.Buffer {
 
 // Put returns buf into bp.
 func (bp *BufferPool) Put(buf *bytes.Buffer) {
+	if buf == nil {
+		return
+	}
+
 	if buf.Cap() < bp.capability {
 		bp.pool.Put(buf)
 	}

core/iox/bufferpool_test.go

@@ -13,3 +13,26 @@ func TestBufferPool(t *testing.T) {
 	pool.Put(bytes.NewBuffer(make([]byte, 0, 2*capacity)))
 	assert.True(t, pool.Get().Cap() <= capacity)
 }
+
+func TestBufferPool_Put(t *testing.T) {
+	t.Run("with nil buf", func(t *testing.T) {
+		pool := NewBufferPool(1024)
+		pool.Put(nil)
+		val := pool.Get()
+		assert.IsType(t, new(bytes.Buffer), val)
+	})
+
+	t.Run("with less-cap buf", func(t *testing.T) {
+		pool := NewBufferPool(1024)
+		pool.Put(bytes.NewBuffer(make([]byte, 0, 512)))
+		val := pool.Get()
+		assert.IsType(t, new(bytes.Buffer), val)
+	})
+
+	t.Run("with more-cap buf", func(t *testing.T) {
+		pool := NewBufferPool(1024)
+		pool.Put(bytes.NewBuffer(make([]byte, 0, 1024<<1)))
+		val := pool.Get()
+		assert.IsType(t, new(bytes.Buffer), val)
+	})
+}