ofxGui / ofxPanel: disableHeader() and .getGroup("g").minimize() are looking bad

    gui_VideoFx.setup("VIDEO FX");
    gui_VideoFx.add(params_VideoFX);

1/ looks fine:

2/ looks bad:

    gui_VideoFx.disableHeader();//BUG
    gui_VideoFx.getGroup("VIDEO FX").minimize();//OK
    gui_VideoFx.getGroup(frag1.parameters.getName()).minimize();//BUG

if the group we like to minimize is nested (not the root group), then it is not minimized fine.
When disabling header it looks strange, like below the next title.

BTW, I am using a modified theme like this:

    //ofxGui theme
    ofxGuiSetFont("fonts/PragmataProR_0822.ttf", 8);
    ofxGuiSetDefaultHeight(18);
    ofxGuiSetBorderColor(16);
    ofxGuiSetFillColor(ofColor(48));
    ofxGuiSetTextColor(ofColor::white);
    ofxGuiSetHeaderColor(ofColor(32));

Start with the ofxGui entry points named in the report: disableHeader(), getGroup(), and minimize(). Reproduce the root and nested-group cases using the shown setup and custom theme, then inspect their rendering behavior. Done means headers disable cleanly and both root and nested groups minimize without visual artifacts.