Ensure correct length of automation patterns in BB editor (LMMS#4212)

When the length of an automation pattern is an integer multiple of one bar, it was displayed with wrong length. This commit fixes the bug.

src/core/AutomationPattern.cpp

@@ -189,7 +189,7 @@ MidiTime AutomationPattern::timeMapLength() const
 {
  if( m_timeMap.isEmpty() ) return 0;
  timeMap::const_iterator it = m_timeMap.end();
- return MidiTime( qMax( MidiTime( (it-1).key() ).getTact() + 1, 1 ), 0 );
+ return MidiTime( MidiTime( (it-1).key() ).nextFullTact(), 0 );
 }