fuzz: Extend descriptor fuzz test

src/test/fuzz/descriptor_parse.cpp

@@ -20,6 +20,11 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     FlatSigningProvider signing_provider;
     std::string error;
     for (const bool require_checksum : {true, false}) {
-        Parse(descriptor, signing_provider, error, require_checksum);
+        const auto desc = Parse(descriptor, signing_provider, error, require_checksum);
+        if (desc) {
+            (void)desc->ToString();
+            (void)desc->IsRange();
+            (void)desc->IsSolvable();
+        }
     }
 }