accounts: don't return reference to string created on the stack

Change-Id: I0216f9beb141230c483271de1ebec0c90f56e438
Reviewed-by: Sébastien Blin <sebastien.blin@savoirfairelinux.com>

lrcinstance.h

@@ -94,10 +94,10 @@ public:
     };
 
     static const std::string& getCurrAccId() {
-        if (!instance().selectedAccountId.empty()) {
-            return instance().selectedAccountId;
+        if (instance().selectedAccountId.empty()) {
+            instance().selectedAccountId = accountModel().getAccountList().at(0);
         }
-        return accountModel().getAccountList()[0];
+        return instance().selectedAccountId;
     };
 
     static void setSelectedAccountId(const std::string& accountId) {

settingswidget.cpp

@@ -480,6 +480,7 @@ SettingsWidget::delAccountSlot()
     delDialog.exec();
 
     if (!LRCInstance::accountModel().getAccountList().size()) {
+        LRCInstance::setSelectedAccountId("");
         emit NavigationRequested(ScreenEnum::WizardScreen);
     }
 }