Fix configuration save with GPS window

[neomilium]

The root cause was that runJavaScript() was being called with an incorrect number of parameters. The PySide6 QWebEnginePage.runJavaScript() signature is:

page.runJavaScript(script, callback)

But the code was passing:

page.runJavaScript(script, self.map.mapWidgetIndex,

This caused the callback to not be properly registered, leading to result getting an empty string or not being called correctly. The fix:

• Removed the self.map.mapWidgetIndex parameter
• Added filtering in the callback to reject None or empty string values

Now it should properly wait for a valid zoom value or timeout and returns the default of 15.