signal 6 (SIGABRT), code -1 (SI_QUEUE) when trying to destruct leveldb::Iterator

I am using leveldb in one [Android project](https://github.com/TGX-Android/leveldb). Here's the file that is used to build `leveldb`: [CMakeLists.txt](https://github.com/TGX-Android/leveldb/blob/main/jni/CMakeLists.txt).

Recently I've upgraded from [c5d5174](https://github.com/google/leveldb/tree/c5d5174a66f02e66d8e30c21ff4761214d8e4d6d) commit to [d019e36](https://github.com/google/leveldb/tree/d019e3605f222ebc5a3a2484a2cb29db537551dd) ([list of changes](https://github.com/google/leveldb/compare/c5d5174...d019e36)) and started receiving a lot of crashes from users during destruction of newly created `leveldb::Iterator` at [db_jni.cpp:465](https://github.com/TGX-Android/leveldb/blob/90be80e80baf31b3521a0749b7fca3bf7102ae77/jni/db_jni.cpp#L465).

Here's the crash log:

```
*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
pid: 0, tid: 0 >>> org.thunderdog.challegram <<<

backtrace:
#00 pc 0000000000089cd0 /apex/com.android.runtime/lib64/bionic/libc.so (abort+164)
#00 pc 00000000000ecff4 /apex/com.android.runtime/lib64/bionic/libc.so (__fortify_fatal(char const*, ...)+124)
#00 pc 00000000000ec4d0 /apex/com.android.runtime/lib64/bionic/libc.so (HandleUsingDestroyedMutex(pthread_mutex_t*, char const*)+52)
#00 pc 00000000000ec318 /apex/com.android.runtime/lib64/bionic/libc.so (pthread_mutex_lock+172)
#00 pc 00000000000bf148 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libc++_shared.so (std::__ndk1::__libcpp_mutex_lock(pthread_mutex_t*)) (SourceCode: /buildbot/src/android/ndk-release-r22/toolchain/llvm-project/libcxx/include/__threading_support:367)
#00 pc 00000000000bf148 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libc++_shared.so (std::__ndk1::mutex::lock()) (SourceCode: /buildbot/src/android/ndk-release-r22/toolchain/llvm-project/libcxx/src/mutex.cpp:33)
#00 pc 000000000002e51c /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::port::Mutex::Lock()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/./port/port_stdcxx.h:55)
#00 pc 000000000002e51c /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::(anonymous namespace)::CleanupIteratorState(void*, void*)) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/db/db_impl.cc:1067)
#00 pc 0000000000040734 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::Iterator::CleanupNode::Run()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/include/leveldb/iterator.h:92)
#00 pc 0000000000040734 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::Iterator::~Iterator()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/table/iterator.cc:16)
#00 pc 0000000000040c48 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::(anonymous namespace)::MergingIterator::~MergingIterator()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/table/merger.cc:27)
#00 pc 0000000000040c48 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::(anonymous namespace)::MergingIterator::~MergingIterator()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/table/merger.cc:27)
#00 pc 0000000000031588 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::(anonymous namespace)::DBIter::~DBIter()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/db/db_iter.cc:62)
#00 pc 0000000000031588 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (leveldb::(anonymous namespace)::DBIter::~DBIter()) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/leveldb/db/db_iter.cc:62)
#00 pc 0000000000018784 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/lib/arm64/libleveldbjni.so (Java_me_vkryl_leveldb_NativeBridge_dbRemoveByPrefix) (SourceCode: /home/vk/tgx/vkryl/leveldb/jni/db_jni.cpp:465)
#00 pc 000000000010b62c /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (art_jni_trampoline+188)
#00 pc 00000000001db6c0 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (me.vkryl.leveldb.LevelDB.N+176)
#00 pc 00000000003205a0 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (de.i.H3+64)
#00 pc 0000000000457550 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (vd.w6.e0+432)
#00 pc 0000000000463e44 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (vd.ya.h2+260)
#00 pc 0000000000134564 /apex/com.android.art/lib64/libart.so (art_quick_invoke_stub+548)
#00 pc 00000000001a9a78 /apex/com.android.art/lib64/libart.so (art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)+200)
#00 pc 000000000032129c /apex/com.android.art/lib64/libart.so (art::interpreter::ArtInterpreterToCompiledCodeBridge(art::Thread*, art::ArtMethod*, art::ShadowFrame*, unsigned short, art::JValue*)+376)
#00 pc 0000000000318688 /apex/com.android.art/lib64/libart.so (bool art::interpreter::DoCall(art::ArtMethod*, art::Thread*, art::ShadowFrame&, art::Instruction const*, unsigned short, art::JValue*)+696)
#00 pc 000000000068d568 /apex/com.android.art/lib64/libart.so (MterpInvokeVirtualQuickRange+540)
#00 pc 0000000000132614 /apex/com.android.art/lib64/libart.so (mterp_op_invoke_virtual_range_quick+20)
#00 pc 00000000008dbc62 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.vdex (vd.o6.od+704)
#00 pc 000000000068cfbc /apex/com.android.art/lib64/libart.so (MterpInvokeVirtualQuick+1344)
#00 pc 0000000000132594 /apex/com.android.art/lib64/libart.so (mterp_op_invoke_virtual_quick+20)
#00 pc 00000000008d9f48 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.vdex (vd.o6.Na+188)
#00 pc 000000000030ebc4 /apex/com.android.art/lib64/libart.so (art::interpreter::Execute(art::Thread*, art::CodeItemDataAccessor const&, art::ShadowFrame&, art::JValue, bool, bool) (.llvm.16619280533006879875)+268)
#00 pc 0000000000674d5c /apex/com.android.art/lib64/libart.so (artQuickToInterpreterBridge+780)
#00 pc 000000000013dff8 /apex/com.android.art/lib64/libart.so (art_quick_to_interpreter_bridge+88)
#00 pc 00000000020056e8 /memfd:jit-cache (vd.o6$k.C2+376)
#00 pc 00000000001f10c8 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (org.drinkless.td.libcore.telegram.Client.h+424)
#00 pc 00000000001f1488 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (org.drinkless.td.libcore.telegram.Client.m+792)
#00 pc 00000000001f1638 /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (org.drinkless.td.libcore.telegram.Client.n+200)
#00 pc 00000000001f1aac /data/app/~~N47gOJXH6paC65XKJsi3BQ==/org.thunderdog.challegram-SVyPef6hxGLByIO5iDtrVg==/oat/arm64/base.odex (org.drinkless.td.libcore.telegram.Client.run+60)
#00 pc 000000000015ce98 /apex/com.android.art/javalib/arm64/boot.oat (java.lang.Thread.run+72)
#00 pc 0000000000134564 /apex/com.android.art/lib64/libart.so (art_quick_invoke_stub+548)
#00 pc 00000000001a9a78 /apex/com.android.art/lib64/libart.so (art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)+200)
#00 pc 000000000055e278 /apex/com.android.art/lib64/libart.so (art::JValue art::InvokeVirtualOrInterfaceWithJValues(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, art::ArtMethod*, jvalue const*)+460)
#00 pc 00000000005ada3c /apex/com.android.art/lib64/libart.so (art::Thread::CreateCallback(void*)+1308)
#00 pc 00000000000eb7a8 /apex/com.android.runtime/lib64/bionic/libc.so (__pthread_start(void*)+64)
#00 pc 000000000008bc8c /apex/com.android.runtime/lib64/bionic/libc.so (__start_thread+64)
```

I haven't yet found the exact change that affected the growth in `signal 6 (SIGABRT), code -1 (SI_QUEUE)` received from users and haven't found a proper way to reproduce the issue (as it seems that it requires `leveldb` to be in a certain state), but it seemed to me to be worthy reporting the finding here, at least if someone else will experience the same issue.