Cache table entry may be null. Let's not assume it's always non-null.

This is done intentionally because we do need correct table index when
resolving external reference. This requires we do need to allocate array
with the same sheet size as the remote document.  But we don't allocate
Table instances for remote sheets that we don't reference, to save
memory.

Change-Id: I27fb6228f0e4558327aa4a04a6bccce8d2f1085f
(cherry picked from commit 3dcfb9a8)

sc/source/ui/docshell/externalrefmgr.cxx

@@ -1122,15 +1122,18 @@ void ScExternalRefCache::getAllCachedDataSpans( sal_uInt16 nFileId, sc::ColumnSp
     const std::vector<TableTypeRef>& rTables = pDocItem->maTables;
     for (size_t nTab = 0, nTabCount = rTables.size(); nTab < nTabCount; ++nTab)
     {
-        const Table& rTable = *rTables[nTab];
+        TableTypeRef pTab = rTables[nTab];
+        if (!pTab)
+            continue;
+
         std::vector<SCROW> aRows;
-        rTable.getAllRows(aRows);
+        pTab->getAllRows(aRows);
         std::vector<SCROW>::const_iterator itRow = aRows.begin(), itRowEnd = aRows.end();
         for (; itRow != itRowEnd; ++itRow)
         {
             SCROW nRow = *itRow;
             std::vector<SCCOL> aCols;
-            rTable.getAllCols(nRow, aCols);
+            pTab->getAllCols(nRow, aCols);
             std::vector<SCCOL>::const_iterator itCol = aCols.begin(), itColEnd = aCols.end();
             for (; itCol != itColEnd; ++itCol)
             {
@@ -1246,8 +1249,11 @@ void ScExternalRefCache::clearCacheTables(sal_uInt16 nFileId)
     std::vector<TableTypeRef>& rTabs = pDocItem->maTables;
     for (size_t i = 0, n = rTabs.size(); i < n; ++i)
     {
-        Table& rTab = *rTabs[i];
-        rTab.clear();
+        TableTypeRef pTab = rTabs[i];
+        if (!pTab)
+            continue;
+
+        pTab->clear();
     }
 
     // Clear the external range name caches.