Add patch to fix potential crash on startup

Raster::resize() was being called with a negative width or height due to
bad state being stored in the config.  This resulted in fldigi crashing
before the UI was displayed.  This patch works around the problem and has
been submitted upstream.

comms/fldigi/Makefile

@@ -2,7 +2,7 @@
 
 PORTNAME=	fldigi
 PORTVERSION=	4.0.17
-PORTREVISION=	2
+PORTREVISION=	3
 CATEGORIES=	comms hamradio
 MASTER_SITES=	SF/${PORTNAME}/${PORTNAME}
 

comms/fldigi/files/patch-src_waterfall_raster.cxx

@@ -0,0 +1,13 @@
+--- src/waterfall/raster.cxx.orig	2018-08-11 23:26:43 UTC
++++ src/waterfall/raster.cxx
+@@ -169,6 +169,10 @@ void Raster::resize(int x, int y, int w,
+ 	while ((Ndest * rhs) < Hdest) Ndest++;
+ 	Ndest--;
+ 
++	if (Wdest < 0)
++		Wdest = 0;
++	if (Hdest < 0)
++		Hdest = 0;
+ 	unsigned char *tempbuf = new unsigned char [Wdest * Hdest];
+ 	unsigned char *oldbuf = vidbuf;
+