patch 8.2.0104: using channel or job with ":execute" has strange effects

Problem:    Using channel or job with ":execute" has strange effects.
Solution:   Give an error message for Job and Channel.
diff --git a/src/eval.c b/src/eval.c
index e0f27a0..f8ba4df 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -6055,7 +6055,15 @@
 	    char_u   buf[NUMBUFLEN];
 
 	    if (eap->cmdidx == CMD_execute)
-		p = tv_get_string_buf(&rettv, buf);
+	    {
+		if (rettv.v_type == VAR_CHANNEL || rettv.v_type == VAR_JOB)
+		{
+		    emsg(_(e_inval_string));
+		    p = NULL;
+		}
+		else
+		    p = tv_get_string_buf(&rettv, buf);
+	    }
 	    else
 		p = tv_stringify(&rettv, buf);
 	    if (p == NULL)
diff --git a/src/testdir/test_eval_stuff.vim b/src/testdir/test_eval_stuff.vim
index ec566da..5362755 100644
--- a/src/testdir/test_eval_stuff.vim
+++ b/src/testdir/test_eval_stuff.vim
@@ -216,3 +216,15 @@
   call assert_fails('source Xversionscript', 'E999:')
   call delete('Xversionscript')
 endfunc
+
+func Test_excute_null()
+  call assert_fails('execute test_null_list()', 'E730:')
+  call assert_fails('execute test_null_dict()', 'E731:')
+  call assert_fails('execute test_null_blob()', 'E976:')
+  execute test_null_string()
+  call assert_fails('execute test_null_partial()', 'E729:')
+  if has('job')
+    call assert_fails('execute test_null_job()', 'E908:')
+    call assert_fails('execute test_null_channel()', 'E908:')
+  endif
+endfunc
diff --git a/src/version.c b/src/version.c
index 54104eb..3362ab5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    104,
+/**/
     103,
 /**/
     102,