Call wtf_init() in fuzzing

fuzz/fuzz-conv.c

@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <gc.h>
 #include "wc.h"
+#include "wtf.h"
 
 char *get_null_terminated(const uint8_t *data, size_t size) {
     char *new_str = (char *)malloc(size+1);
@@ -28,6 +29,13 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size){
 	GC_set_oom_fn(die_oom);
 #else
 	GC_oom_fn = die_oom;
+#endif
+#ifdef USE_M17N
+#ifdef USE_UNICODE
+	wtf_init(WC_CES_UTF_8, WC_CES_UTF_8);
+#else
+	wtf_init(WC_CES_EUC_JP, WC_CES_EUC_JP);
+#endif
 #endif
 	init_done = 1;
     }