Gazebo 11 ignores links with mass smaller than 1e-5

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I am not sure if this is a bug or intended behavior. Gazebo 11 ignores a link if it has a small mass value. This link is added to the robot (has mass equal to 1e-5):

<link name="test_link">
  <inertial>
    <origin xyz="0 0 0" rpy="0 0 0"/>
    <mass value="1e-5"/>
    <inertia ixx="1e-9" ixy="1e-9" ixz="1e-9" iyy="1e-9" iyz="1e-9" izz="1e-9"/>
  </inertial>
  <visual>
    <origin xyz="0 1 0" rpy="0 0 0"/>
    <geometry>
      <sphere radius="0.2" />
    </geometry>
  </visual>
</link>

However, if I change mass value to 1e-6, the link is not displayed any more (neither visually, nor in the list of model links):

<link name="test_link">
  <inertial>
    <origin xyz="0 0 0" rpy="0 0 0"/>
    <mass value="1e-6"/>
    <inertia ixx="1e-9" ixy="1e-9" ixz="1e-9" iyy="1e-9" iyz="1e-9" izz="1e-9"/>
  </inertial>
  <visual>
    <origin xyz="0 1 0" rpy="0 0 0"/>
    <geometry>
      <sphere radius="0.2" />
    </geometry>
  </visual>
</link>