Throw instead of UB if ending wrong parallel for

debugging/vov-bug-finder/kp_view_of_views_bug_finder.cpp

@@ -18,6 +18,7 @@
 
 #include <atomic>
 #include <cstdint>
+#include <exception>
 #include <iostream>
 #include <mutex>
 #include <optional>
@@ -82,7 +83,12 @@ extern "C" void kokkosp_begin_parallel_for(char const *kernelName,
 
 extern "C" void kokkosp_end_parallel_for(uint64_t kernelID) {
   std::lock_guard lock(current_mutex);
-  current.erase(current.find(kernelID));
+  auto it = current.find(kernelID);
+  if (it == current.end()) {
+    throw std::runtime_error(
+        "Bug: attempting to end a parallel_for that is not \"running\"");
+  }
+  current.erase(it);
 
   if (verbose) {
     std::cout << "end kernel " << kernelID << '\n';