cmake: replace an outlier `set(var)` with `set(var, "")`

For consistency with the rest of these expressions and readability.

Closes #20305

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b0daa102d3658252dc3202c3822211f472f56add..e70d47563c71cd515336a4952357817d00c59d92 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,7 +36,7 @@ if(NOT "$ENV{CURL_BUILDINFO}$ENV{CURL_CI}$ENV{CI}" STREQUAL "")
       get_property(_cache_var_type CACHE ${_cache_var} PROPERTY TYPE)
       get_property(_cache_var_value CACHE ${_cache_var} PROPERTY VALUE)
       if(_cache_var_type STREQUAL "UNINITIALIZED")
-        set(_cache_var_type)
+        set(_cache_var_type "")
       else()
         set(_cache_var_type ":${_cache_var_type}")
       endif()