Fixed issue 578 - corrected type usage

src/zmq_utils.cpp

@@ -148,8 +148,8 @@ uint8_t *zmq_z85_decode (uint8_t *dest, char *string)
     }
     unsigned int byte_nbr = 0;
     unsigned int char_nbr = 0;
+    unsigned int string_len = strlen (string);
     uint32_t value = 0;
-    uint string_len = strlen (string);
     while (char_nbr < string_len) {
         //  Accumulate value in base 85
         value = value * 85 + decoder [(uint8_t) string [char_nbr++] - 32];