patch 8.1.0011: maparg() and mapcheck() confuse empty and non-existing

Problem:    maparg() and mapcheck() confuse empty and non-existing.
Solution:   Return <Nop> for an existing non-empty mapping. (closes #2940)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 5cee976..46e55b3 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -7383,7 +7383,12 @@
     {
 	/* Return a string. */
 	if (rhs != NULL)
-	    rettv->vval.v_string = str2special_save(rhs, FALSE);
+	{
+	    if (*rhs == NUL)
+		rettv->vval.v_string = vim_strsave((char_u *)"<Nop>");
+	    else
+		rettv->vval.v_string = str2special_save(rhs, FALSE);
+	}
 
     }
     else if (rettv_dict_alloc(rettv) != FAIL && rhs != NULL)
diff --git a/src/testdir/test_maparg.vim b/src/testdir/test_maparg.vim
index 9ad8383..0fb878b 100644
--- a/src/testdir/test_maparg.vim
+++ b/src/testdir/test_maparg.vim
@@ -29,9 +29,13 @@
         \ maparg('foo', '', 0, 1))
 
   map abc x<char-114>x
-  call assert_equal(maparg('abc'), "xrx")
+  call assert_equal("xrx", maparg('abc'))
   map abc y<S-char-114>y
-  call assert_equal(maparg('abc'), "yRy")
+  call assert_equal("yRy", maparg('abc'))
+
+  map abc <Nop>
+  call assert_equal("<Nop>", maparg('abc'))
+  unmap abc
 endfunction
 
 function Test_range_map()
diff --git a/src/version.c b/src/version.c
index 7cf8d16..3ebeb77 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    11,
+/**/
     10,
 /**/
     9,