could not open world file

edit

world file

<?xml version="1.0"?>
    <sdf version="1.6">
      <world name="default">
        <include>
          <uri>model://ground_plane</uri>
        </include>
        <include>
          <uri>model://sun</uri>
        </include>
        <model name="my_mesh">
          <pose>-80 -80 0  0 0 0</pose>
          <static>true</static>
          <link name="body">
            <visual name="visual">
              <geometry>
                <mesh><uri>file://model.dae</uri></mesh>
              </geometry>
            </visual>
          </link>
        </model>
      </world>
    </sdf>

this is file

<launch>
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="city.world"/>
    <arg name="verbose" value="true"/>
  </include>
</launch>

this is my launch file

when I launch this it shows me an error as

[Err] [Server.cc:379] Could not open file[city.world]

but when spawn using

gazebo city.world

there is no error and it's spawning correctly. what could be the problem?