Fix randomx cache selection for RPCs

Was using the wrong cache slot, and returning invalid PoW hashes to RPC clients

src/crypto/rx-slow-hash.c

@@ -243,14 +243,17 @@ void rx_slow_hash(const uint64_t mainheight, const uint64_t seedheight, const ch
   CTHR_MUTEX_LOCK(rx_mutex);
 
   /* if alt block but with same seed as mainchain, no need for alt cache */
-  if (is_alt && s_height == seedheight && !memcmp(rx_s[toggle].rs_hash, seedhash, sizeof(rx_s[toggle].rs_hash)))
-    is_alt = 0;
-
+  if (is_alt) {
+    if (s_height == seedheight && !memcmp(rx_s[toggle].rs_hash, seedhash, sizeof(rx_s[toggle].rs_hash)))
+      is_alt = 0;
+	else
+	  toggle ^= 1;
+  } else {
   /* RPC could request an earlier block on mainchain */
-  if (!is_alt && s_height > seedheight)
-    is_alt = 1;
+    if (s_height > seedheight)
+      is_alt = 1;
+  }
 
-  toggle ^= (is_alt != 0);
   if (toggle != rx_toggle)
     changed = 1;
   rx_toggle = toggle;