Bug#719523: [PATCH] Fix start-up segfault (active_modem == NULL)

[Kamal Mostafa <kamal@canonical.com>]

BugLink: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=719523

Do not let the waterfall init code dereference global 'active_modem' before
it's been set.  Note though, there are plenty of other suspicious blind
dereferences of active_modem in waterfall.cxx and probably elsewhere.  :-(
---
 src/waterfall/waterfall.cxx | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/waterfall/waterfall.cxx b/src/waterfall/waterfall.cxx
index 1ae0bd2..eaf3113 100644
--- a/src/waterfall/waterfall.cxx
+++ b/src/waterfall/waterfall.cxx
@@ -1545,7 +1545,8 @@ void waterfall::USB(bool b) {
 	if (wfdisp->USB() == b)
 		return;
 	wfdisp->USB(b);
-	active_modem->set_reverse(reverse);
+	if (likely(active_modem))
+		active_modem->set_reverse(reverse);
 	REQ(&viewer_redraw);
 }
 
-- 
1.8.1.2