Fix SIGABRT in IsFileNotFound (e.g. when creating an empty database)

While on it:
- Add USES=gnome due to complaint in check-sanity

PR:		232030
Reported by:	korsani@free.fr
MFH:		2018Q4

audio/musicpd/Makefile

@@ -2,7 +2,7 @@
 
 PORTNAME=	musicpd
 PORTVERSION=	0.20.21
-PORTREVISION=	2
+PORTREVISION=	3
 CATEGORIES=	audio ipv6
 MASTER_SITES=	http://www.musicpd.org/download/mpd/${PORTVERSION:R}/
 DISTNAME=	mpd-${PORTVERSION}
@@ -18,7 +18,7 @@ BROKEN_powerpc64=	Does not build on powerpc64
 LIB_DEPENDS=	libboost_iostreams.so:devel/boost-libs \
 		libicudata.so:devel/icu
 
-USES=		compiler:c++14-lang gmake pkgconfig tar:xz
+USES=		compiler:c++14-lang gmake gnome pkgconfig tar:xz
 
 GNU_CONFIGURE=	yes
 USE_GNOME=	glib20

audio/musicpd/files/patch-src_input_Error.hxx

@@ -0,0 +1,10 @@
+--- src/input/Error.hxx.orig	2018-07-06 17:17:27 UTC
++++ src/input/Error.hxx
+@@ -30,7 +30,6 @@
+  * exist?  This function attempts to recognize exceptions thrown by
+  * various input plugins.
+  */
+-gcc_pure
+ bool
+ IsFileNotFound(std::exception_ptr e);
+