fix(core): nil-check resolveProcess callback and tun_interface

Backport chen08209#1996 (TuTouPower). Two-layer defence against the
':remote' core process SIGABRT that hits ~2s after VPN start on Android
14+ when the ':remote' subprocess is killed and respawned: Go side does
not invoke a nil callback, C++ side does not call JNI methods on a null
jobject.

Author: oviron

android/core/src/main/cpp/core.cpp

@@ -105,6 +105,9 @@ call_tun_interface_resolve_process_impl(void *tun_interface, const int protocol,
                                         const char *source,
                                         const char *target,
                                         const int uid) {
+    if (tun_interface == nullptr) {
+        return strdup("");
+    }
     ATTACH_JNI();
     const auto packageName = reinterpret_cast<jstring>(env->CallObjectMethod(
             static_cast<jobject>(tun_interface),

core/lib.go

@@ -84,7 +84,7 @@ func (th *TunHandler) handleResolveProcess(source, target net.Addr) string {
 	_ = th.limit.Acquire(context.Background(), 1)
 	defer th.limit.Release(1)
 
-	if th.listener == nil {
+	if th.listener == nil || th.callback == nil {
 		return ""
 	}
 	var protocol int