JFJochReceiverRugnux: after a cancel, an analysed frame still waits for a send slot

A cancel promises that the frames already received are analysed, merged and written, but the wait for a
slot gave up on cancelled, so the first frame after a cancel to find the image buffer full was lost.
The wait keeps its bound of 2 s, which is what protects the teardown.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HVeDQsU5a8AJUdJPgWevAK

receiver/JFJochReceiverRugnux.cpp

@@ -504,7 +504,7 @@ ZeroCopyReturnValue *JFJochReceiverRugnux::AnalysedImageSlot() {
     constexpr auto WRITER_WAIT = std::chrono::seconds(2);
     const auto t0 = std::chrono::steady_clock::now();
     auto loc = image_buffer.GetImageSlot();
-    while (loc == nullptr && !cancelled && std::chrono::steady_clock::now() - t0 < WRITER_WAIT) {
+    while (loc == nullptr && std::chrono::steady_clock::now() - t0 < WRITER_WAIT) {
         std::this_thread::sleep_for(std::chrono::milliseconds(1));
         loc = image_buffer.GetImageSlot();
     }