Empty box showing up in my installer? How do I remove it?

Answer 1

That box is for the section description.

Take a look at the Modern UI Basic.nsi file:

;--------------------------------
;Installer Sections

Section "Dummy Section" SecDummy

  SetOutPath "$INSTDIR"

  ;ADD YOUR OWN FILES HERE...

  ;Store installation folder
  WriteRegStr HKCU "Software\Modern UI Test" "" $INSTDIR

  ;Create uninstaller
  WriteUninstaller "$INSTDIR\Uninstall.exe"

SectionEnd

;--------------------------------
;Descriptions

  ;Language strings
  LangString DESC_SecDummy ${LANG_ENGLISH} "A test section."

  ;Assign language strings to sections
  !insertmacro MUI_FUNCTION_DESCRIPTION_BEGIN
    !insertmacro MUI_DESCRIPTION_TEXT ${SecDummy} $(DESC_SecDummy)
  !insertmacro MUI_FUNCTION_DESCRIPTION_END

Read more Modern UI Readme, section on Components page descriptions.

The Modern UI components page has a text box in which a description can be shown when the user hovers the mouse over a component. If you don't want to use these descriptions, insert the MUI_COMPONENTSPAGE_NODESC interface setting.

To set a description for a section, an additional parameter needs to be added to Section commmand with a unique identifier for the section. This name can later be used to set the description for this section.

Answer 2

If you want to remove it, !define MUI_COMPONENTSPAGE_NODESC at the top of your script