segfault when calling a mockito spy

I have a similar issue as described in #411.

The test crashes when calling the method of a mockito spy object.
I am have tested this with j2objc 1.3.1 .

```
import org.junit.Test;
import java.io.StringWriter;
import org.mockito.Mockito;
import java.util.ArrayList;
import java.util.List;
public class MockitoTest {

@Test
public void test() throws Exception {
List spyList = Mockito.spy(new ArrayList());

spyList.add("one");

Mockito.verify(spyList).add("one");
}
}
```
```
JUnit version 4.11
.Error: signal 11:
0 Tests 0x000000010e921095 signalHandler + 39
1 libsystem_platform.dylib 0x00007fff971fd52a _sigtramp + 26
2 CoreFoundation 0x00007fff8aecb1f2 __CFStringCreateImmutableFunnel3 + 2978
3 CoreFoundation 0x00007fff8af4a2e2 ___forwarding___ + 514
4 CoreFoundation 0x00007fff8af4a058 _CF_forwarding_prep_0 + 120
5 Tests 0x000000010e920d25 -[MockitoTest test] + 101
6 CoreFoundation 0x00007fff8af4b9cc __invoking___ + 140
7 CoreFoundation 0x00007fff8af4b85e -[NSInvocation invoke] + 286
8 Tests 0x000000010e8a0f9b -[JavaLangReflectMethod invoke:object:] + 23
9 Tests 0x000000010e8a0bdd -[JavaLangReflectMethod invokeWithId:withNSObjectArray:] + 326
10 Tests 0x000000010e8c4bba -[OrgJunitInternalRunnersModelReflectiveCallable run] + 19
11 Tests 0x000000010e8d3aea -[OrgJunitRunnersParentRunner runLeafWithOrgJunitRunnersModelStatement:withOrgJunitRunnerDescription:withOrgJunitRunnerNotificationRunNotifier:] + 64
12 Tests 0x000000010e8d39d7 OrgJunitRunnersParentRunner_runChildrenWithOrgJunitRunnerNotificationRunNotifier_ + 376
13 Tests 0x000000010e8d3e25 -[OrgJunitRunnersParentRunner runWithOrgJunitRunnerNotificationRunNotifier:] + 85
14 Tests 0x000000010e8d39d7 OrgJunitRunnersParentRunner_runChildrenWithOrgJunitRunnerNotificationRunNotifier_ + 376
15 Tests 0x000000010e8d3e25 -[OrgJunitRunnersParentRunner runWithOrgJunitRunnerNotificationRunNotifier:] + 85
16 Tests 0x000000010e8cc12c -[OrgJunitRunnerJUnitCore runWithOrgJunitRunnerRunner:] + 154
17 Tests 0x000000010e8cbe52 OrgJunitRunnerJUnitCore_runMainWithOrgJunitInternalJUnitSystem_withNSStringArray_ + 669
18 Tests 0x000000010e8cbabc OrgJunitRunnerJUnitCore_runMainAndExitWithOrgJunitInternalJUnitSystem_withNSStringArray_ + 32
19 CoreFoundation 0x00007fff8af4b9cc __invoking___ + 140
20 CoreFoundation 0x00007fff8af4b85e -[NSInvocation invoke] + 286
21 Tests 0x000000010e8a0f9b -[JavaLangReflectMethod invoke:object:] + 23
22 Tests 0x000000010e8a0bdd -[JavaLangReflectMethod invokeWithId:withNSObjectArray:] + 326
23 Tests 0x000000010e921330 main + 326
24 libdyld.dylib 0x00007fff973715ad start + 1
25 ??? 0x0000000000000003 0x0 + 3

```