Added 'add_plug' arg in sensor_d435 to resolve instantiation error

stretch_description/urdf/stretch_d435i.xacro

@@ -2,6 +2,7 @@
 <robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="stretch_d435i">
 
   <xacro:arg name="use_nominal_extrinsics" default="true"/>
+  <xacro:arg name="add_plug" default="false"/>
   <xacro:include filename="$(find realsense2_description)/urdf/_d435.urdf.xacro"/>
 
   <!-- xyz = "
@@ -9,7 +10,7 @@
        up and down (- down / + up)
        sideways (- right / + left)
        " -->
-  <xacro:sensor_d435 parent="link_head_tilt" use_nominal_extrinsics="$(arg use_nominal_extrinsics)">
+  <xacro:sensor_d435 parent="link_head_tilt" use_nominal_extrinsics="$(arg use_nominal_extrinsics)" add_plug="$(arg add_plug)">
     <origin
       xyz="0.03 -0.0122 0.0182"
       rpy="0.0 0.0 0.0" />