Bug: need twice pop(context) to close touchCallback dialogs

**Describe the bug**
Don't know if it's me but after i upgraded fl_chart from 0.69.2 to 0.70.2, when i touch an axis-based chart on mobile to open a dialog, i need to pop(context) a few times to close it.

**To Reproduce**
Some code snippet below:
```dart
...barTouchData: BarTouchData(
touchCallback: (FlTouchEvent event, response) {
if (response == null || response.spot == null) return;
final barTouchedIndex = response.spot!.touchedBarGroupIndex;
_showSitenamesBarChart(barTouchedIndex);
},
...

// where _showSitenamesBarChart() eventually shows a dialog:
void _showSitenamesBarChart(int barTouchedIndex) {
...
showDialog(
context: context,
builder: (context) => AlertDialog(
...
actions: [
ElevatedButton(
onPressed: () => Navigator.pop(context),
child: Text("Ok"),
),
]));
}
```

**Screenshots**
https://github.com/user-attachments/assets/4082a10a-24dc-450b-92f9-be0ff85d3ad5

**Versions**
Flutter version 3.29.2

Start by reproducing the issue with the BarTouchData touchCallback and showDialog example on Flutter 3.29.2, checking how the chart handles touch events after the dialog opens. Trace the callback and navigation behavior around the touched bar. Done means the dialog closes with a single Navigator.pop(context) and the regression is covered by a test or reproducible case.

Written by the indexing model from the issue text.