patch 8.2.3479: crash when calling job_start with an invalid argument

Problem:    Crash when calling job_start with an invalid argument. (Virginia
            Senioria)
Solution:   Clear the first item in argv. (closes #8957)

src/misc2.c

@@ -2953,6 +2953,7 @@ build_argv_from_list(list_T *l, char ***argv, int *argc)
 
 	    for (i = 0; i < *argc; ++i)
 		VIM_CLEAR((*argv)[i]);
+	    (*argv)[0] = NULL;
 	    return FAIL;
 	}
 	(*argv)[*argc] = (char *)vim_strsave(s);

src/testdir/test_channel.vim

@@ -2362,5 +2362,9 @@ func Test_parse_messages_in_autocmd()
   augroup END
 endfunc
 
+func Test_job_start_with_invalid_argument()
+  call assert_fails('call job_start([0zff])', 'E976:')
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3479,
 /**/
     3478,
 /**/