patch 8.2.4672: using :normal with Ex mode may make :substitute hang

Problem:    Using :normal with Ex mode may make :substitute hang.
Solution:   When getting an empty line behave like 'q' was typed.
            (closes #10070)

src/ex_cmds.c

@@ -4233,6 +4233,11 @@ ex_substitute(exarg_T *eap)
 			    {
 				typed = *resp;
 				vim_free(resp);
+				// When ":normal" runs out of characters we get
+				// an empty line.  Use "q" to get out of the
+				// loop.
+				if (ex_normal_busy && typed == NUL)
+				    typed = 'q';
 			    }
 			}
 			else

src/testdir/test_normal.vim

@@ -2641,6 +2641,15 @@ func Test_normal33_g_cmd2()
   bw!
 endfunc
 
+func Test_normal_ex_substitute()
+  " This was hanging on the substitute prompt.
+  new
+  call setline(1, 'a')
+  exe "normal! gggQs/a/b/c\<CR>"
+  call assert_equal('a', getline(1))
+  bwipe!
+endfunc
+
 " Test for g CTRL-G
 func Test_g_ctrl_g()
   new

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4672,
 /**/
     4671,
 /**/