Fix (unlikely) integer overflow error in writedata(..)

The range check was applied before padding up, in the unlikely case
sizes (INT_MAX - 2) or (INT_MAX - 1) were passed in,
the value overflow into a negative integer.

source/blender/blenloader/intern/writefile.cc

@@ -704,14 +704,14 @@ static void writedata(WriteData *wd, int filecode, size_t len, const void *adr)
     return;
   }
 
+  /* Align to 4 (writes uninitialized bytes in some cases). */
+  len = (len + 3) & ~size_t(3);
+
   if (len > INT_MAX) {
     BLI_assert_msg(0, "Cannot write chunks bigger than INT_MAX.");
     return;
   }
 
-  /* Align to 4 (writes uninitialized bytes in some cases). */
-  len = (len + 3) & ~size_t(3);
-
   /* Initialize #BHead. */
   bh.code = filecode;
   bh.old = adr;