fix CMake warning about uninit KDSingleApplication_LIBRARY_QTID

Author: Allen Winter

CMakeLists.txt

@@ -98,11 +98,12 @@ endif()
 if(${PROJECT_NAME}_QT6)
     find_package(QT NAMES Qt6 REQUIRED)
     set(${PROJECT_NAME}_LIBRARY_QTID "-qt6")
+    set(KDSingleApplication_LIBRARY_QTID ${${PROJECT_NAME}_LIBRARY_QTID})
 else()
     find_package(QT NAMES Qt5 REQUIRED)
     set(${PROJECT_NAME}_LIBRARY_QTID "")
+    set(KDSingleApplication_LIBRARY_QTID "")
 endif()
-set(KDSingleApplication_LIBRARY_QTID ${${PROJECT_NAME}_LIBRARY_QTID})
 find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core Network Widgets)
 
 if(${PROJECT_NAME}_TESTS)