Crash dropping images on layers

[sentry]

Sentry Issue: ASEPRITE-2PY

EXC_BAD_ACCESS / KERN_INVALID_ADDRESS / 0x0: Fatal Error: EXC_BAD_ACCESS / KERN_INVALID_ADDRESS / 0x0
  File "context.cpp", line 97, in app::Context::range
    onGetActiveSite(&site);
  File "cmd_transaction.cpp", line 132, in app::CmdTransaction::isDocRangeEnabled
    return context()->range().enabled();
  File "cmd_transaction.cpp", line 84, in app::CmdTransaction::onExecute
    if (isDocRangeEnabled()) {
  File "cmd.cpp", line 39, in app::Cmd::execute
    onExecute();
  File "transaction.cpp", line 60, in app::Transaction::Transaction
    m_cmds->execute(m_ctx);
...
(29 additional frame(s) were not displayed)

[dacap]

Highly probable this is due the new Context::range(). I'll take this tomorrow.

[martincapello]

I have this fix:

bool CmdTransaction::isDocRangeEnabled() const
{
  return (context() ? context()->range().enabled() : false);
}

This is because the source documents loaded in the DropOnTimeline command are loaded without a context, so it is null once isDocRangeEnabled is called.