Fix calculation of columnDate

The returned date of columnDate was not correct in certain circumstances
so that the price information using this date was incorrect which
resulted in false opening balance values in reports.

BUG: 414932
FIXED-IN: 5.0.8

kmymoney/plugins/views/reports/core/pivottable.cpp

@@ -1330,9 +1330,15 @@ int PivotTable::columnValue(const QDate& _date) const
 
 QDate PivotTable::columnDate(int column) const
 {
-  if (m_config.isColumnsAreDays())
-    return m_beginDate.addDays(m_config.columnPitch() * column - m_startColumn);
-  else
+  if (m_config.isColumnsAreDays()) {
+    // The m_config.columnPitch() return value is defined as 'unsigned int'.
+    // We need to cast this to an 'int' here, because if column is zero (e.g.
+    // for the opening balance) and m_startColumn is one, the result of the
+    // subtraction should be -1 (the day before m_beginDate), but since it
+    // is treated as 'unsigned int' a very large value is added resulting in a
+    // date way in the future.
+    return m_beginDate.addDays(static_cast<int>(m_config.columnPitch() * column) - m_startColumn);
+  } else
     return m_beginDate.addMonths(m_config.columnPitch() * column).addDays(-m_startColumn);
 }