Fix schedule_all completion for empty ranges

include/exec/static_thread_pool.hpp

@@ -1746,6 +1746,12 @@ namespace experimental::execution
         void start() & noexcept
         {
           std::size_t size         = items_.size();
+          if (size == 0)
+          {
+            STDEXEC::set_value(static_cast<Receiver&&>(this->rcvr_));
+            return;
+          }
+
           std::size_t nthreads     = this->pool_.available_parallelism();
           bwos_params params       = this->pool_.params();
           std::size_t local_size   = params.blockSize * params.numBlocks;

test/exec/test_static_thread_pool.cpp

@@ -1,8 +1,10 @@
 #include "catch2/catch_all.hpp"
+#include <exec/sequence/ignore_all_values.hpp>
 #include <exec/static_thread_pool.hpp>
 #include <stdexec/execution.hpp>
 
 #include <mutex>
+#include <ranges>
 #include <thread>
 #include <unordered_set>
 namespace ex = STDEXEC;
@@ -45,6 +47,16 @@ TEST_CASE("bulk on static_thread_pool executes on multiple threads", "[types][st
   REQUIRE(thread_ids.size() == num_of_threads);
 }
 
+TEST_CASE("schedule_all on static_thread_pool handles empty ranges",
+          "[types][static_thread_pool]")
+{
+  exec::static_thread_pool pool{2};
+  auto sender = exec::schedule_all(pool, std::views::iota(size_t{0}, size_t{0}))
+              | exec::ignore_all_values();
+
+  CHECK(ex::sync_wait(std::move(sender)));
+}
+
 TEST_CASE("bulk on static_thread_pool executes on multiple threads, take 2",
           "[types][static_thread_pool]")
 {