Fix game mode crash: null-guard node in HandleEditEvent

[willwade]

Problem

DasherApp build 32 on TestFlight hit a crash (1 of 4 total) when entering game mode:

EXC_BAD_ACCESS (SIGSEGV) at 0x0000000000000054

Thread 0 Crashed:
0   CGameModule::HandleEditEvent(type, strText, node) + 36
1   CScreenGameModule::HandleEditEvent(type, strText, node) + 28
2   std::function<...>::operator()(...)
3   CDasherInterfaceBase::editOutput(strText, node)
4   CSymbolNode::Do()

User comment: "Started game mode". Crash fires when the first character is typed after entering game mode.

Root cause

TextOutputAction::execute (ControlManager.cpp:212) passes nullptr as the cause node:

void TextOutputAction::execute(CDasherInterfaceBase* intf) {
    intf->editOutput(m_text, nullptr);   // ← nullptr as pCause
}

This nullptr propagates through OnEditEvent.Broadcast → CGameModule::HandleEditEvent. The game module then dereferences node->offset() unconditionally, crashing at address 0x54 (the offset of m_Offset within CDasherNode when this is null):

void CGameModule::HandleEditEvent(..., CDasherNode* node) {
    if (!m_pAlph) return;
    const int iOffset(node->offset());  // ← node is nullptr → SIGSEGV at 0x54

This is the normal character-typing path: CSymbolNode::Do() → TextOutputAction::execute → editOutput(text, nullptr). Every regular character triggers it; the crash only manifests in game mode because HandleEditEvent is the subscriber that actually dereferences node.

Fix

Add a null guard at the top of HandleEditEvent:

if (!node) return;

A null-node edit event carries no useful information for game-mode tracking (which needs the node offset to verify the user typed the correct target character). Dropping it is safe.

1 insertion, 0 deletions. No API changes.

Verification

• clang-format: clean
• Register dump from the crash confirms x3 (the node parameter) was 0x0000000000000000

Related

The TextOutputAction::execute passing nullptr is by design — actions don't have access to the triggering node. An alternative fix would be threading the node through the action system, but that's a much larger change for no user-visible benefit. The null guard in HandleEditEvent is the right level.