Cannot raise sliced underground view level in Extended

**Steps to reproduce**

1. Start a game in Extended using the last release.
2. Switch to sliced view (`Ctrl+U` or `View...` submenu)

**Expected results**

You can raise the level displayed Sliced Underground View by pressing `(` or using the tool in the `View...` submenu.

**Actual results**

The `Build industry` window opens instead, due to tool conflict:

When you turn Sliced Underground View off, you still cannot see higher levels due to an unrelated bug in Extended. In order to see them you must restart the game.

**Comments**
This was observed in the 0.6 RC release; I have not tested the latest GitHub commit.

Start by reproducing the issue in Simutrans Extended using the listed sliced-view steps and the `(` shortcut or View submenu tool. Trace the conflict with the Build industry window and the unrelated level-display behavior; done means the level can be raised in sliced underground view and higher levels remain visible without restarting.

Written by the indexing model from the issue text.