DLS will fail to bind methods to default declarations when they contain invalid defaults

[JonatanWaern]

Replicates via

template foo {
    method foo_method() default {
        default(); // invalid, but should not break overrides from below code
    }
}

template foo_2 is foo {
    method foo_method() {
        default(); // goto-def here should find foo_method in foo template, but does not
    }
}

is foo_2;

Removing the 'default' decl in foo_method fixes the issue. From logs the difference is that we fail to map the cursor position to a symbol in the failing case.