Screen sharing crashes on Linux due to hotkey parser bug (Zoom 7.0, Ubuntu 24.04, Wayland)

**Environment:**
- Zoom 7.0.0.1666 (native .deb)
- Ubuntu 24.04.4 LTS, GNOME 46.0, Wayland session
- Intel Lunar Lake GPU (Mesa 25.2.8)
- Dual monitor: 1920x1080 at 1x scale + 3840x2160 at 1.5x scale

**Steps to reproduce:**
1. Install Zoom 7.0.0.1666 on Ubuntu 24.04 with a Wayland session
2. Ensure `shortcut_as_global_ShortcutID_ShowHideFloatingMeetingControls=true` in `~/.config/zoomus.conf` (this is the default)
3. Join a meeting
4. Click "Share Screen"
5. Zoom crashes within a few seconds

**Expected behavior:** Screen sharing starts normally.

**Actual behavior:** Zoom aborts with SIGABRT. The stderr log shows:

```
terminate called after throwing an instance of 'std::invalid_argument'
  what():  stoi
zoom was exited due to a handled signal: 6
```

**Root cause analysis:**

Clicking "Share Screen" triggers hotkey registration via the `com.zoom.HotKeyService` D-Bus service. GDB analysis shows the crash occurs while processing the `<Ctrl><Alt><Shift>H` hotkey binding (Show/Hide Floating Meeting Controls). The hotkey parser produces an empty string that is passed to `std::stoi("")`, which throws `std::invalid_argument`. The exception is uncaught, causing `std::terminate()` → `abort()`.

Stack trace (abbreviated):
```
#0  __pthread_kill_implementation (signo=6)
#3  __GI_raise (sig=6)
#4  __GI_abort
#7  std::terminate()
#8  __cxa_throw
#9  std::__throw_invalid_argument("stoi")
#10-#13  Zoom binary (hotkey parsing)
#14 libgio-2.0.so (D-Bus response handler)
#33 g_main_context_iteration
#34 QEventDispatcherGlib::processEvents
```

**Workaround:**

Edit `~/.config/zoomus.conf` and set:
```
shortcut_as_global_ShortcutID_ShowHideFloatingMeetingControls=false
```

Then restart Zoom. Screen sharing works normally with this change. The only side effect is losing the Ctrl+Alt+Shift+H global shortcut.

**Notes:**
- Also reproduces with `xwayland=false` (native Wayland mode)
- Also reproduces with `QT_ENABLE_HIGHDPI_SCALING=0` and `QT_SCALE_FACTOR=1`
- The bug was not present in Zoom 6.7.2 (same system, same config)