Application throws fatal exception and crashes app on connecting wifi and selecting proxy configuration

[passbrains]

Adapted from ​https://www.passbrains.com/dashboard/view-ticket.php?ticket_no=AAN-3

Environment

Asus Nexus 7 Android 4.4.3 KitKat
Rooted device: No
ABP version 1.2.1.331 build# 331

How to reproduce

1. Download the ABP app
2. Install the ABP app on the android device
3. Ensure android device is not connected to a wifi connection before launching the app
4. Launch the ABP application
5. Connect to a wifi connection
6. Select 'AdBlock Plus' from the Android status bar
7. The 'AdBlock Plus' settings are displayed
8. Toggle the 'Filtering' button from 'ON' to 'OFF' and back to 'ON'
9. Message box appears informing user about setting proxy settings manually, select 'Configure'
10. Observe message from Android: 'Unfortunately, Adblock Plus has stopped.'

Observed behaviour

The application crashes and fatal exception is thrown:

07-24 23:23:52.549 E/AndroidRuntime(22601): FATAL EXCEPTION: main

07-24 23:23:52.549 E/AndroidRuntime(22601): Process: org.adblockplus.android, PID: 22601

07-24 23:23:52.549 E/AndroidRuntime(22601): java.lang.IllegalStateException: Could not execute method of the activity

See attached log file.

Expected behaviour

The user should be able to select 'Configure' and the the Proxy configuration screen should display.

[rjeschke]

The crash should no longer occur, still it's not an optimal solution as there's no feedback when opening the Proxy configuration dialogue fails.

Anyway, the main cause is fixed, will revisit this later for beautification.