Fix crash on clear option for automation tracks (#3195). Also fix state change signalling so that lines reappear on undoing a clear.

git-svn-id: svn://localhost/ardour2/branches/3.0@7178 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/automation_time_axis.cc

@@ -385,11 +385,10 @@ AutomationTimeAxisView::set_interpolation (AutomationList::InterpolationStyle st
 void
 AutomationTimeAxisView::clear_clicked ()
 {
-	_session->begin_reversible_command (_("clear automation"));
 	if (_line) {
+		_session->begin_reversible_command (_("clear automation"));
 		_line->clear ();
 	}
-	_session->commit_reversible_command ();
 }
 
 void

libs/ardour/automation_list.cc

@@ -338,7 +338,7 @@ AutomationList::deserialize_events (const XMLNode& node)
 		maybe_signal_changed ();
 	}
 
-        ControlList::thaw ();
+        thaw ();
         
 	return 0;
 }
@@ -391,7 +391,7 @@ AutomationList::set_state (const XMLNode& node, int version)
 			fast_simple_add (x, y);
 		}
 
-                ControlList::thaw ();
+                thaw ();
 
 		return 0;
 	}

libs/evoral/src/ControlList.cpp

@@ -167,8 +167,9 @@ ControlList::maybe_signal_changed ()
 {
 	mark_dirty ();
 
-	if (_frozen)
+	if (_frozen) {
 		_changed_when_thawed = true;
+	}
 }
 
 void