op-node: conf depth filter should not filter out genesis (#3042)

op-node/rollup/driver/conf_depth.go

@@ -30,7 +30,7 @@ func (c *confDepth) L1BlockRefByNumber(ctx context.Context, num uint64) (eth.L1B
 	// TODO: performance optimization: buffer the l1Head, invalidate any reorged previous buffer content,
 	// and instantly return the origin by number from the buffer if we can.
 
-	if c.depth == 0 || num+c.depth <= c.l1Head().Number {
+	if num == 0 || c.depth == 0 || num+c.depth <= c.l1Head().Number {
 		return c.L1Fetcher.L1BlockRefByNumber(ctx, num)
 	}
 	return eth.L1BlockRef{}, ethereum.NotFound

op-node/rollup/driver/conf_depth_test.go

@@ -53,6 +53,7 @@ func TestConfDepth(t *testing.T) {
 		{name: "two conf not like 1", head: 4, req: 3, depth: 2, pass: false},
 		{name: "two conf pass", head: 4, req: 2, depth: 2, pass: true},
 		{name: "easy pass", head: 100, req: 20, depth: 5, pass: true},
+		{name: "genesis case", head: 0, req: 0, depth: 4, pass: true},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, tc.Run)