Fix crash in my recently-added autocorrect check

autotests/parsertest.cpp

@@ -86,6 +86,7 @@ private Q_SLOTS:
         T("Mar 01-Mar Su[-2] Mo 17:00-18:00; PH off");
         T("Oct Su[-1]-Dec 31 08:00-18:00");
         T("Oct Su[-1]-Dec 31 Su 08:00-18:00");
+        T("Mar Su[1]-Oct Su[1]: 11:00-20:00; PH 11:00-20:00");
 
         // from https://wiki.openstreetmap.org/wiki/Key:opening_hours#Simple_examples
         T("Mo-Fr 08:00-17:30");

src/lib/openinghours.cpp

@@ -107,7 +107,7 @@ void OpeningHoursPrivate::autocorrect()
             else if (rule->selectorCount() == prevRule->selectorCount()
                      && rule->m_timeSelector
                      && prevRule->m_timeSelector
-                     && rule->selectorCount() == 2 && rule->m_weekdaySelector
+                     && rule->selectorCount() == 2 && rule->m_weekdaySelector && prevRule->m_weekdaySelector
                      // slower than writing an operator==, but so much easier to write :)
                      && rule->m_weekdaySelector->toExpression() == prevRule->m_weekdaySelector->toExpression()
                      ) {