TextEditor: Fix crash after request provider destruction

If an assist provider gets destructed while a code assist request is
running we need to cancel the running request and reset the provider.
Otherwise we might try to cast the deleted provider in
CodeAssistantPrivate::isDestroyEvent. Which is called whenever the
texteditor is changed.

Fixes: QTCREATORBUG-31563
Change-Id: Iaec36c6ca73ba5e6795c1c3847da8b30fd446ffc
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/texteditor/codeassist/codeassistant.cpp

@@ -183,6 +183,8 @@ void CodeAssistantPrivate::requestProposal(AssistReason reason,
 
     m_assistKind = kind;
     m_requestProvider = provider;
+    connect(
+        m_requestProvider, &QObject::destroyed, this, &CodeAssistantPrivate::cancelCurrentRequest);
     IAssistProcessor *processor = provider->createProcessor(assistInterface.get());
     processor->setAsyncCompletionAvailableHandler([this, reason, processor](
                                                   IAssistProposal *newProposal) {
@@ -367,6 +369,8 @@ void CodeAssistantPrivate::invalidateCurrentRequestData()
 {
     m_processor = nullptr;
     m_requestProvider = nullptr;
+    disconnect(
+        m_requestProvider, &QObject::destroyed, this, &CodeAssistantPrivate::cancelCurrentRequest);
     m_receivedContentWhileWaiting = false;
 }