rpc: minize getTipHash() calls in gbt

Set tip at the start of the function and only update it for a long poll.

Additionally have getTipHash return an optional, so the
caller can explicitly check that a tip exists.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/node/interfaces.cpp b/src/node/interfaces.cpp
index 2633ff1b98..68c1c598cd 100644
--- a/src/node/interfaces.cpp
+++ b/src/node/interfaces.cpp
@@ -847,11 +847,11 @@ public:
         return chainman().GetParams().IsTestChain();
     }
 
-    uint256 getTipHash() override
+    std::optional<uint256> getTipHash() override
     {
         LOCK(::cs_main);
         CBlockIndex* tip{chainman().ActiveChain().Tip()};
-        if (!tip) return uint256{0};
+        if (!tip) return {};
         return tip->GetBlockHash();
     }