[isolate] Remove unused exception handle

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 1aad57632f4d9bc2593d6df5f08578ef8085e3f4..bf0f533f5162fbca439d0d9b15f3aa00f9f3e8f9 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2990,7 +2990,11 @@ void Isolate::RunMicrotasks() {
   v8::Isolate::SuppressMicrotaskExecutionScope suppress(
       reinterpret_cast<v8::Isolate*>(this));
   is_running_microtasks_ = true;
-  RunMicrotasksInternal();
+  MaybeHandle<Object> maybe_exception;
+  MaybeHandle<Object> result = Execution::TryCall(
+      this, microtask_run(), factory()->undefined_value(), 0, NULL,
+      &maybe_exception);
+  //RunMicrotasksInternal();
   is_running_microtasks_ = false;
   FireMicrotasksCompletedCallback();
 }
@@ -3021,7 +3025,6 @@ void Isolate::RunMicrotasksInternal() {
             &maybe_exception);
         handle_scope_implementer_->LeaveMicrotaskContext();
         // If execution is terminating, just bail out.
-        Handle<Object> exception;
         if (result.is_null() && maybe_exception.is_null()) {
           // Clear out any remaining callbacks in the queue.
           heap()->set_microtask_queue(heap()->empty_fixed_array());