ros2_control: No parameter file provided. Configuration might be wrong. failed to parse input yaml file(s)

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Hello. I am trying to build a 4 wheel differential drive robot. But i am getting error when using ros2_control.

Version: Ros2 Foxy

Terminal Output

[robot_state_publisher-1] Parsing robot urdf xml string.

[robot_state_publisher-1] Link chassis had 0 children

[robot_state_publisher-1] Link left_back_wheel had 0 children

[robot_state_publisher-1] Link left_front_wheel had 0 children

[robot_state_publisher-1] Link right_back_wheel had 0 children

[robot_state_publisher-1] Link right_front_wheel had 0 children

".yaml" Config File for Ros2 Control

controller_manager: ros__parameters: update_rate: 30 use_sim_time: true

diff_cont:
  type: diff_drive_controller/DiffDriveController

joint_broad:
  type: joint_state_broadcaster/JointStateBroadcaster

diff_cont: ros__parameters:

publish_rate: 50.0

base_frame_id: base_link

left_wheel_names: ['left_front_wheel_joint', 'left_back_wheel_joint']
right_wheel_names: ['right_front_wheel_joint', 'right_back_wheel_joint']
wheel_separation: 0.36
wheel_radius: 0.1

use_stamped_vel: false

Main URDF File --> robot_core.xacro

<robot <a="" href="http://xmlns:xacro="http://www.ros.org/wiki/xacro">xmlns:xacro="http://www.ros.org/wiki/..." ><="" p=""> </robot>

<xacro:include filename="inertial_macros.xacro"/>

<material name="white">
    <color rgba="1 1 1 1" />
</material>

<material name="orange">
    <color rgba="1 0.3 0.1 1" />
</material>

<material name="blue">
    <color rgba="0.2 0.2 1 1" />
</material>

<material name="black">
    <color rgba="0 0 0 1" />
</material>


<!-- BASE LINK -->
<link name="base_link">

</link>


<!-- CHASSI LINK -->
<joint name="chassis_joint" type="fixed">
    <parent link="base_link"/>
    <child link="chassis"/>
    <origin xyz="-0.1 0 0"/>
</joint>

<link name="chassis">
    <visual>
        <!-- <origin xyz="0.15 0 0.075"/>   # This line is used to move the chasis relative to its link -->
        <geometry>
            <box size="0.5 0.3 0.05"/>
        </geometry>
        <material name="white"/>
    </visual>

    <collision>
        <!-- <origin xyz="0.3 0 0.075"/>   0.15 0 0.075 -->
        <geometry>
            <box size="0.5 0.3 0.3"/>
        </geometry>
    </collision>

    <xacro:inertial_box mass="0.5" x="0.5" y="0.3" z="0.05">
        <origin xyz="0 0 0" rpy="0 0 0"/>
    </xacro:inertial_box>
</link>

<gazebo reference="chassis">
    <material>Gazebo/Orange</material>
</gazebo>

<!-- LEFT FRONT WHEEL LINK -->
<joint name="left_front_wheel_joint" type="continuous">
    <parent link="base_link"/>
    <child link="left_front_wheel"/>        
    <origin xyz="0.15 0.18 0" rpy="-${pi/2} 0 0"/>
    <axis xyz="0 0 1"/>
</joint>

<link name="left_front_wheel">
    <visual>
        <geometry>
            <cylinder radius="0.1" length="0.04"/>
        </geometry>
        <material name="blue"/>
    </visual>
    <collision>
        <geometry>
            <cylinder radius="0.1" length="0.04"/>
        </geometry>
    </collision>

    <xacro:inertial_cylinder mass="0.1" length="0.04" radius="0.1">
        <origin xyz="0 0 0" rpy="0 0 0"/>
    </xacro:inertial_cylinder>
</link>

<gazebo reference="left_front_wheel">
    <material>Gazebo/Blue</material>
</gazebo>

<!-- RIGHT FRONT WHEEL LINK -->
<joint name="right_front_wheel_joint" type="continuous">
    <parent link="base_link"/>
    <child link="right_front_wheel"/>        
    <origin xyz="0.15 -0.18 0" rpy="${pi/2} 0 0"/>
    <axis xyz="0 0 -1"/>
</joint>

<link ...