This means you have a function named wp_my_admin_enqueue_scripts hooked to an action, either in your theme or a plugin, but that function name is not available to WordPress for some reason.
When that action fires, any functions “hooked” to it are executed by WordPress. If one of the hooked functions is not available, this is the error presented.
For example, in the sample code below the function named sc_corporate_widgets_init is executed when WordPress fires the widgets_init action.
add_action( 'widgets_init', 'sc_corporate_widgets_init' );
Make sure you do not have a spelling error with a function name. They must match exactly in order to prevent this error.