Potential Bug with App Designed to Create Subplots of Polar Axes?

I am trying to programmatically generate a set of polar subplots in my Matlab application. It seems to work almost perfectly, but when I generate polar axis subplots in my app, an empty figure window is generated at the first subplot call (and none of the others). I thought I had left a 'figure' command in my code somewhere, but that is not the problem. I have included a minimally functional reproduction of the problem in the pasted code below (this site won't allow me to attach a file with the .mlapp extension). I tried adding a breakpoint at the first 'ax1 = subplot(2...' call and then stepping into the subplot function, but the figure window pops up as soon as the debugger jumps into that function. I am at a loss and want to know if I have messed something up, or if this is a bug that needs fixing.

The example application below contains one button, whose callback function generates the subplots.

Please let me know if you need more details to answer this question.

-Michael

classdef subplottestapp < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure                        matlab.ui.Figure
        Panelwithsubplotsofpolaraxes    matlab.ui.container.Panel
        CallpolarsubplotfunctionButton  matlab.ui.control.Button
    end

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: CallpolarsubplotfunctionButton
        function CallpolarsubplotfunctionButtonPushed(app, event)
        %%%%%%%%%%%%%%%%%%THIS IS THE CODE THAT NEEDS ASSESSMENT
        
        %Required to turn off auto resize for subplots. 
        %See: https://www.mathworks.com/help/matlab/creating_guis/graphics-support-in-app-designer.html
        app.Panelwithsubplotsofpolaraxes.AutoResizeChildren = 'off';    
        
        %Plot in the panel
        plotparent = app.Panelwithsubplotsofpolaraxes;
        %Create two subplots, each with polar axes
        %Adapted from: https://www.mathworks.com/help/matlab/creating_guis/graphics-support-in-app-designer.html
        ax1 = subplot(2,1,1,polaraxes,'Parent',plotparent);
        polarplot(ax1,360*rand(5,1)*pi/180,rand(5,1)); 
        ax2 = subplot(2,1,2,polaraxes,'Parent',plotparent);
        polarplot(ax2,360*rand(5,1)*pi/180,rand(5,1)); 
        
        %%%%%%%%%%%%%%%%%%THIS IS THE CODE THAT NEEDS ASSESSMENT
        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 360 464];
            app.UIFigure.Name = 'UI Figure';

            % Create Panelwithsubplotsofpolaraxes
            app.Panelwithsubplotsofpolaraxes = uipanel(app.UIFigure);
            app.Panelwithsubplotsofpolaraxes.Title = 'Panel with subplots of polar axes';
            app.Panelwithsubplotsofpolaraxes.Position = [1 1 360 464];

            % Create CallpolarsubplotfunctionButton
            app.CallpolarsubplotfunctionButton = uibutton(app.Panelwithsubplotsofpolaraxes, 'push');
            app.CallpolarsubplotfunctionButton.ButtonPushedFcn = createCallbackFcn(app, @CallpolarsubplotfunctionButtonPushed, true);
            app.CallpolarsubplotfunctionButton.Position = [186 413 157 22];
            app.CallpolarsubplotfunctionButton.Text = 'Call polar subplot function';

            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = subplottestapp

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end