chore(cmake): guard test_nglpdfwidget by TARGET nglwidgets to avoid linking if library missing\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Z/src/nglwidgets/CMakeLists.txt

@@ -61,7 +61,7 @@ NGL_TARGET_LINK_LIBRARIES(nglwidgets
 NGL_INSTALL_TARGET(nglwidgets)
 
 # Unit test for PDFWidget
-IF(BUILD_TESTING)
+IF(BUILD_TESTING AND TARGET nglwidgets)
   FIND_PACKAGE(Qt6 REQUIRED COMPONENTS Test Widgets)
   ADD_EXECUTABLE(test_nglpdfwidget test_nglpdfwidget.cpp)
   TARGET_LINK_LIBRARIES(test_nglpdfwidget PRIVATE nglwidgets Qt6::Test Qt6::Widgets)