patch 8.2.4828: fix for unmapping simplified key not fully tested

Problem:    Fix for unmapping simplified key not fully tested.
Solution:   Add a test case. (closes #10292)

src/map.c

@@ -726,6 +726,8 @@ do_map(
 				    mpp = &(mp->m_next);
 				    continue;
 				}
+				// In keyround for simplified keys, don't unmap
+				// a mapping without m_simplified flag.
 				if (keyround1_simplified && !mp->m_simplified)
 				    break;
 				// We reset the indicated mode bits. If nothing

src/testdir/test_mapping.vim

@@ -1627,7 +1627,7 @@ func Test_mouse_drag_insert_map()
   set mouse&
 endfunc
 
-func Test_unmap_simplfied()
+func Test_unmap_simplifiable()
   map <C-I> foo
   map <Tab> bar
   call assert_equal('foo', maparg('<C-I>'))
@@ -1636,6 +1636,11 @@ func Test_unmap_simplfied()
   call assert_equal('', maparg('<C-I>'))
   call assert_equal('bar', maparg('<Tab>'))
   unmap <Tab>
+
+  map <C-I> foo
+  unmap <Tab>
+  " This should not error
+  unmap <C-I>
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4828,
 /**/
     4827,
 /**/