feat: refactored some pci code and added pretty print of classes

kernel/libc/kprintf.c

@@ -9,7 +9,7 @@
 #include <libk/kprint.h>
 #include <libk/libk.h>
 #include <types.h>
-
+const char* printf_null_str = "NULL";
 /*
  * Integer to string
  */
@@ -46,7 +46,10 @@ uint32_t vasprintf(char *buf, const char *fmt, va_list args) {
         }
         switch (fmt[i]) {
             case 's': { // string
-                char *s_fmt = (char *) va_arg(args, char*);
+                const char *s_fmt = (char *) va_arg(args, char*);
+                if (s_fmt == NULL) {
+                    s_fmt = printf_null_str;
+                }
                 while (*s_fmt) {
                     buf[ptr++] = *s_fmt++;
                 }