clipboard: Return early if check_clipboard_size_limits() fails
clipboard: Return early if check_clipboard_size_limits() fails

b0a2ff4 "clipboard: Add fixup_clipboard_text helper"
mistakenly removed some early returns when text conversion fails for
some reason. This commit readds it.

Signed-off-by: Christophe Fergeau <05b95054a663c388a4e33d95828cb30f0370f8ef@redhat.com>
Signed-off-by: Pavel Grunt <fbda40b445316123f12a5a6bd7556918ea74f4bc@redhat.com>

fgouget/spice-gtk,flexVDI/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk,fgouget/spice-gtk