Add missing boundary check to grok_infnan

The grok_infnan() function was walking past the end of the string
while skipping over trailing '0' characters. This another variation
of Perl#17370.

numeric.c

@@ -784,7 +784,7 @@ Perl_grok_infnan(pTHX_ const char** sp, const char* send)
                 s++; if (s == send || isALPHA_FOLD_NE(*s, 'Y')) return fail;
                 s++;
             } else if (odh) {
-                while (*s == '0') { /* 1.#INF00 */
+                while (s < send && *s == '0') { /* 1.#INF00 */
                     s++;
                 }
             }