fix boundary case for _dictNextPower

src/dict.c

@@ -949,7 +949,7 @@ static unsigned long _dictNextPower(unsigned long size)
 {
     unsigned long i = DICT_HT_INITIAL_SIZE;
 
-    if (size >= LONG_MAX) return LONG_MAX;
+    if (size >= LONG_MAX) return LONG_MAX + 1LU;
     while(1) {
         if (i >= size)
             return i;