fix: fix uninitialized variable

undefined behavior sanitizer complained about uninitialized variable:
src/widget/form/chatform.cpp:781:9: runtime error: load of value 190, which is not a valid value for type 'bool'

src/widget/form/genericchatform.cpp

@@ -133,6 +133,7 @@ GenericChatForm::GenericChatForm(const Contact* contact, QWidget* parent)
     : QWidget(parent, Qt::Window)
     , audioInputFlag(false)
     , audioOutputFlag(false)
+    , searchAfterLoadHistory(false)
 {
     curRow = 0;
     headWidget = new ChatFormHeader();