fuzz: increase FromHex() coverage

src/test/fuzz/hex.cpp

@@ -10,6 +10,7 @@
 #include <uint256.h>
 #include <univalue.h>
 #include <util/strencodings.h>
+#include <util/transaction_identifier.h>
 
 #include <cassert>
 #include <cstdint>
@@ -27,7 +28,11 @@ FUZZ_TARGET(hex)
         assert(ToLower(random_hex_string) == hex_data);
     }
     (void)IsHexNumber(random_hex_string);
-    (void)uint256::FromHex(random_hex_string);
+    if (uint256::FromHex(random_hex_string)) {
+        assert(random_hex_string.length() == 64);
+        assert(Txid::FromHex(random_hex_string));
+        assert(Wtxid::FromHex(random_hex_string));
+    }
     (void)uint256S(random_hex_string);
     try {
         (void)HexToPubKey(random_hex_string);