When use pulsar::Message msg = pulsar::MessageBuilder().setContent(sMsg).build() to Create Message, sometimes it will occur segment fault #476

(gdb) bt
#0 pop (this=0x7f2b58df7900) at pulsar-client-3.4/lib/ObjectPool.h:74
#1 allocate (this=0x7f2b58df7900) at pulsar-client-3.4/lib/ObjectPool.h:134
#2 allocate (n=1, this=) at pulsar-client-3.4/lib/ObjectPool.h:167
#3 allocate (__a=, __n=1) at /usr/local/gcc-4.9.3/include/c++/4.9.3/bits/alloc_traits.h:357
#4 __shared_count<pulsar::MessageImpl, pulsar::Allocator<pulsar::MessageImpl, 100000> > (__a=..., this=0x7f2b3e589ea8)
at /usr/local/gcc-4.9.3/include/c++/4.9.3/bits/shared_ptr_base.h:616
#5 __shared_ptr<pulsar::Allocator<pulsar::MessageImpl, 100000> > (__a=..., __tag=..., this=0x7f2b3e589ea0,
this@entry=<error reading variable: Cannot access memory at address 0x7f2b3e589e98>)
at /usr/local/gcc-4.9.3/include/c++/4.9.3/bits/shared_ptr_base.h:1090
#6 shared_ptr<pulsar::Allocator<pulsar::MessageImpl, 100000> > (__a=..., __tag=..., this=0x7f2b3e589ea0)
at /usr/local/gcc-4.9.3/include/c++/4.9.3/bits/shared_ptr.h:316
#7 allocate_shared<pulsar::MessageImpl, pulsar::Allocator<pulsar::MessageImpl, 100000> > (__a=...)
at /usr/local/gcc-4.9.3/include/c++/4.9.3/bits/shared_ptr.h:588
#8 create (this=0x2622ba0 pulsar::messagePool) at pulsar-client-3.4/lib/ObjectPool.h:212
#9 pulsar::MessageBuilder::createMessageImpl () at pulsar-client-3.4/lib/MessageBuilder.cc:42

(gdb) print head_
Cannot access memory at address 0x7f2b58df7900
(gdb) print result
$1 = (void *) 0x1

void* pop() {
if (!head_) {
// size = 0
std::lock_guardstd::mutex lock(mutex_);

            if (!globalPool_) {
                return NULL;
            }

            GlobalPool* poolEntry = globalPool_;
            head_ = globalPool_->node_;
            pushSize_ += globalPool_->nodeCount_;
            globalNodeCount_ -= globalPool_->nodeCount_;
            globalPool_ = globalPool_->next_;
            delete poolEntry;
        }
        void* result = head_;
        if (result) {
            head_ = head_->next;
            pushSize_--;
        }
        return result;
    }