Wrong indentation on if-then with comments

Comments at the end of this `if` makes the `then` block to not get indented.
```
if (prd.source()
.isPresent()) // exclude generated productions like casts
prd = null;
```
Line 331. IntelliJ reports this as well.
I think the problem comes from the if condition that got split into two lines. If I move the comment to a separate line, then indentation works as expected.

首先檢查第331行附近的 formatter 原始碼，並使用拆分的 if 條件和尾隨註解重現所回報的程式碼片段。追蹤 then 區塊的縮排如何計算，接著為此情況新增或更新涵蓋率，並確認格式化後的輸出是否正確縮排 prd。

由索引模型根據 Issue 內容生成。