only access first element if vector is not empty, fdo#55734

Change-Id: I60db486195e7216968dc8c7c7c0c79fb7e8c1b88
diff --git a/sc/source/core/tool/dbdata.cxx b/sc/source/core/tool/dbdata.cxx
index bb5475c..a6e6364 100644
--- a/sc/source/core/tool/dbdata.cxx
+++ b/sc/source/core/tool/dbdata.cxx
@@ -455,7 +455,9 @@ bool ScDBData::HasQueryParam() const

bool ScDBData::HasSortParam() const
{
    return mpSortParam && mpSortParam->maKeyState[0].bDoSort;
    return mpSortParam &&
        !mpSortParam->maKeyState.empty() &&
        mpSortParam->maKeyState[0].bDoSort;
}

bool ScDBData::HasSubTotalParam() const