file_systems/QueryParser.h: Fix -Werror=maybe-uninitialized

Fix fPosition and fTerm not being initialized when expr is NULL
at line 1162.
Pointed out by GCC14.

Change-Id: If883ac0cc32e3418d0e3b49b42012efd861d65f4
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7641
Haiku-Format: Haiku-format Bot <no-reply+haikuformatbot@haiku-os.org>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

headers/private/file_systems/QueryParser.h

@@ -1158,6 +1158,9 @@ Equation<QueryPolicy>::PrintToStream()
 
 template<typename QueryPolicy>
 Expression<QueryPolicy>::Expression(char* expr)
+	:
+	fPosition(NULL),
+	fTerm(NULL)
 {
 	if (expr == NULL)
 		return;