[cmake] Fix uninstall failure when no config is specified.

uninstall.cmake

@@ -52,5 +52,5 @@ endmacro(_SETUP_PROJECT_UNINSTALL)
 # it is going to be called first See the first paragraph here
 # https://cmake.org/cmake/help/latest/command/install.html#introduction
 install(
-  CODE "execute_process(COMMAND \"${CMAKE_COMMAND}\" --build \"${PROJECT_BINARY_DIR}\" --config \${CMAKE_INSTALL_CONFIG_NAME} --target uninstall)"
+  CODE "if (\${CMAKE_INSTALL_CONFIG_NAME})\n  execute_process(COMMAND \"${CMAKE_COMMAND}\" --build \"${PROJECT_BINARY_DIR}\" --config \${CMAKE_INSTALL_CONFIG_NAME} --target uninstall)\nendif()"
 )