Handle negative timeout for waitTipChanged()

src/interfaces/mining.h

@@ -93,7 +93,8 @@ public:
      *
      * @param[in] current_tip block hash of the current chain tip. Function waits
      *                        for the chain tip to differ from this.
-     * @param[in] timeout     how long to wait for a new tip
+     * @param[in] timeout     how long to wait for a new tip (default is forever)
+     *
      * @returns               Hash and height of the current chain tip after this call.
      */
     virtual BlockRef waitTipChanged(uint256 current_tip, MillisecondsDouble timeout = MillisecondsDouble::max()) = 0;

src/node/interfaces.cpp

@@ -1072,6 +1072,8 @@ public:
 
     BlockRef waitTipChanged(uint256 current_tip, MillisecondsDouble timeout) override
     {
+        Assume(timeout >= 0ms); // No internal callers should use a negative timeout
+        if (timeout < 0ms) timeout = 0ms;
         if (timeout > std::chrono::years{100}) timeout = std::chrono::years{100}; // Upper bound to avoid UB in std::chrono
         {
             WAIT_LOCK(notifications().m_tip_block_mutex, lock);