Don't show clipboard error when we're trying to show the File > New dialog

The error is confusing because the user doesn't know that we're trying
to access the clipboard info only to fill Width/Height fields
automatically on File > New. Some errors (like "invalid image format")
should be displayed only when we use Edit > Paste explicitly.

src/app/util/clipboard_native.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2021  Igara Studio S.A.
+// Copyright (C) 2021-2022  Igara Studio S.A.
 // Copyright (C) 2016-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -36,12 +36,28 @@ using namespace base::serialization::little_endian;
 
 namespace {
   clip::format custom_image_format = 0;
+  bool show_clip_errors = true;
+
+  class InhibitClipErrors {
+    bool m_saved;
+  public:
+    InhibitClipErrors() {
+      m_saved = show_clip_errors;
+      show_clip_errors = false;
+    }
+    ~InhibitClipErrors() {
+      show_clip_errors = m_saved;
+    }
+  };
 
   void* native_display_handle() {
     return os::instance()->defaultWindow()->nativeHandle();
   }
 
   void custom_error_handler(clip::ErrorCode code) {
+    if (!show_clip_errors)
+      return;
+
     switch (code) {
       case clip::ErrorCode::CannotLock:
         ui::Alert::show(Strings::alerts_clipboard_access_locked());
@@ -289,6 +305,10 @@ bool get_native_clipboard_bitmap(doc::Image** image,
 
 bool get_native_clipboard_bitmap_size(gfx::Size* size)
 {
+  // Don't show errors when we are trying to get the size of the image
+  // only. (E.g. don't show "invalid image format error")
+  InhibitClipErrors inhibitErrors;
+
   clip::image_spec spec;
   if (clip::get_image_spec(spec)) {
     size->w = spec.width;

src/clip

@@ -1 +1 @@
-Subproject commit c46c49141f72dd753b260eea4e6d7b37413f0ff6
+Subproject commit 2ada8b17b39bf41a669248a2be5c6e4be4c27f14