fix: prevent crash by ensuring there is active section on app start

If `activeSectionId` does point to section that is not restored
correctly (by any reason), then the app will crash. That's becasue code
assumes there is always an active section set and it will try to
reference null item in this case.

fixes: #8785

src/app/modules/main/module.nim

@@ -472,7 +472,7 @@ method load*[T](
 
   # Set active section on app start
   # If section is profile then open chat by default
-  if activeSection.sectionType == SectionType.ProfileSettings:
+  if activeSection.isEmpty() or activeSection.sectionType == SectionType.ProfileSettings:
     self.setActiveSection(self.view.model().getItemBySectionType(SectionType.Chat))
   else:
     self.setActiveSection(activeSection)