Fix logic with spline target detection

CMakeLists.txt

@@ -69,7 +69,7 @@ if (ITA_BASE_WITH_OLD_RAVEN_OPS)
 				"ITABase old RAVEN ops requires regular expressions and old config implementation. Please activate."
 		)
 	endif ()
-	if (TARGET Spline::spline)
+	if (NOT TARGET Spline::spline)
 		message (FATAL_ERROR "ITABase old RAVEN ops requires SPLINE, which was not found. Please provide.")
 	endif ()
 endif ()