Fix formatting in tor_assertf() message in struct_check_magic().

Closes 32771; bugfix on 0.4.2.1-alpha.

changes/bug32771

@@ -0,0 +1,4 @@
+  o Minor bugfixes (logging, crash):
+    - Avoid a possible crash when trying to log a (fatal) assertion failure
+      about mismatched magic numbers in configuration objects. Fixes bug 32771;
+      bugfix on 0.4.2.1-alpha.

src/lib/confmgt/structvar.c

@@ -53,8 +53,8 @@ struct_check_magic(const void *object, const struct_magic_decl_t *decl)
   const uint32_t *ptr = STRUCT_VAR_P(object, decl->magic_offset);
   tor_assertf(*ptr == decl->magic_val,
               "Bad magic number on purported %s object. "
-              "Expected %"PRIu32"x but got "PRIu32"x.",
-              decl->magic_val, *ptr);
+              "Expected %"PRIu32"x but got %"PRIu32"x.",
+              decl->typename, decl->magic_val, *ptr);
 }
 
 /**