compose: Make a function to hide compose error.

This commit creates compose_error.hide() function that
can be used to hide compose_error alerts.

frontend_tests/node_tests/compose_error.js

@@ -17,4 +17,11 @@ run_test("compose_error_test", () => {
     assert.equal($("#compose-send-button").prop("disabled"), false);
     assert.ok(!$("#sending-indicator").visible());
     assert.ok($("#compose-textarea").is_focused());
+
+    $("#compose-send-status").fadeOut = (prop) => {
+        assert.equal(prop, 500);
+        return "none";
+    };
+
+    compose_error.hide();
 });

static/js/click_handlers.js

@@ -14,6 +14,7 @@ import * as buddy_data from "./buddy_data";
 import * as channel from "./channel";
 import * as compose from "./compose";
 import * as compose_actions from "./compose_actions";
+import * as compose_error from "./compose_error";
 import * as compose_state from "./compose_state";
 import {media_breakpoints_num} from "./css_variables";
 import * as emoji_picker from "./emoji_picker";
@@ -609,7 +610,7 @@ export function initialize() {
     // COMPOSE
 
     $("body").on("click", "#compose-send-status .compose-send-status-close", () => {
-        $("#compose-send-status").stop(true).fadeOut(500);
+        compose_error.hide();
     });
 
     $("body").on("click", ".empty_feed_compose_stream", (e) => {

static/js/compose_error.js

@@ -20,3 +20,7 @@ export function show_not_subscribed(error_html, bad_input) {
     show(error_html, bad_input, "home-error-bar");
     $(".compose-send-status-close").hide();
 }
+
+export function hide() {
+    $("#compose-send-status").stop(true).fadeOut(500);
+}