Wayland: Fix fallback decorations emitting errors

A GLFW_CURSOR_UNAVAILABLE error would be emitted each time the cursor
moved over the fallback decorations if the standard cursor shape
appropriate for that part was missing on the system.

These errors served no useful purpose and have been removed.

(cherry picked from commit 00a663dafd)

src/wl_window.c

@@ -1358,11 +1358,8 @@ static void setCursor(_GLFWwindow* window, const char* name)
 
     cursor = wl_cursor_theme_get_cursor(theme, name);
     if (!cursor)
-    {
-        _glfwInputError(GLFW_PLATFORM_ERROR,
-                        "Wayland: Standard cursor shape unavailable");
         return;
-    }
+
     // TODO: handle animated cursors too.
     image = cursor->images[0];