tools/xenalyze: Fix -Werror=nonnull failure

GCC 15.2 with Alpine Linux 3.24 fails with -Werror=nonnull, complaining that
we're calling bzero(NULL, 128).

This is a legitimate diagnostic.  xenalyze has it's own error() function
shadowing the standard library one, and can in principle return when p is
NULL.

Extend the check in error() with ERR_MAX_TOLERABLE to short circuit the
variable tolerance check.

Suggested-by: Anthony PERARD <anthony.perard@vates.tech>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

tools/xentrace/xenalyze.c

@@ -8767,7 +8767,7 @@ void dump_raw(const char * s, struct record_info *ri)
 
 void error(enum error_level l, struct record_info *ri)
 {
-    if ( l > opt.tolerance )
+    if ( l > ERR_MAX_TOLERABLE || l > opt.tolerance )
     {
         if ( ri )
             dump_generic(warn, ri);