microptimization: reduce number of calls to BoxedFrame::handleFrameExit

by decrefing frame_info->exc earlier this will less often be true:
if (frame->ob_refcnt > 1)
    frame->handleFrameExit();

src/runtime/frame.cpp

@@ -271,6 +271,12 @@ extern "C" void deinitFrame(FrameInfo* frame_info) noexcept {
         PyErr_Clear();
     }
 
+    if (frame_info->exc.type) {
+        Py_CLEAR(frame_info->exc.type);
+        Py_CLEAR(frame_info->exc.value);
+        Py_CLEAR(frame_info->exc.traceback);
+    }
+
     assert(cur_thread_state.frame_info == frame_info);
     cur_thread_state.frame_info = frame_info->back;
     BoxedFrame* frame = frame_info->frame_obj;
@@ -289,12 +295,6 @@ extern "C" void deinitFrame(FrameInfo* frame_info) noexcept {
 
     Py_CLEAR(frame_info->boxedLocals);
 
-    if (frame_info->exc.type) {
-        Py_CLEAR(frame_info->exc.type);
-        Py_CLEAR(frame_info->exc.value);
-        Py_CLEAR(frame_info->exc.traceback);
-    }
-
     Py_CLEAR(frame_info->globals);
 
     assert(!PyErr_Occurred());