[debugger][android] Fixing single step inside Exception on Android (mono/mono#16596)

[debugger][android] Fixing single step inside Exception on Android (mono/mono#16596)

* Fixing single step inside Exception on Android...
The method is null because on ss_create_init_args the IL is -1 when calling method Mono_UnhandledException_internal what I think it's expected, because of that I ignore the single step on android if there is no method. (debugger-engine.c)
After that the sequence point cannot be found because it's calling a method of class DynamicMethodNameCounter what I think it's expected, because of that I remove the assert on android. (debugger-agent.c)
Fixes mono/mono#14772

* Changing comment to make it clear...

Commit migrated from https://github.com/mono/mono/commit/1046dd746f3f99e97f034a2c2b51bdb4e19128ae