heightmap insertion unsuccessful with gazebo 7

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I want to use heightmap created by myself in gazebo, and I`ve followed tutorials like this one and this. I use Ubuntu 16.04 and gazebo 7 as the second tutorial requires.

At first , I created a heightmap as the first tutorial instructed, and I tested with my gazebo. It worked out, though occasionally the heightmap wasn't loaded fully . Only half of the terrain was loaded, and the other half was flat.

But after a few hours I tried again. But no matter how I try , my gazebo always crashes after I insert heightmap. And the error msg is always the same:

gzclient: /usr/include/boost/smart_ptr/shared_ptr.hpp:648: typename boost::detail::sp_member_access<T>::type boost::shared_ptr<T>::operator->() const [with T = gazebo::msgs::Response; typename boost::detail::sp_member_access<T>::type = gazebo::msgs::Response*]: Assertion `px != 0' failed.

I've checked a question asked by others before.But is there any better solution to this problem? Updating gazebo to 8 may work, but it's not convenient and the tutorials insert heightmap with gazebo 7 successfully.

Thanks in advance.