justify range to prevent negative tab span and memory alloc, rhbz#1057741

I could not reproduce the crash of that bug (probably having more memory
available), but the backtrace had nTabSpan = -2 implicitly casted to
size_t leading to allocation of a huge amount of memory with
vector::reserve(), which ScRange::Justify() exactly prevents.

Change-Id: Idb79e1be62649922ba793cab01e00011479fade9

sc/source/ui/docshell/externalrefmgr.cxx

@@ -2078,6 +2078,7 @@ ScExternalRefCache::TokenArrayRef ScExternalRefManager::getDoubleRefTokensFromSr
     }
 
     ScRange aRange(rRange);
+    aRange.Justify();
     SCTAB nTabSpan = aRange.aEnd.Tab() - aRange.aStart.Tab();
 
     vector<ScExternalRefCache::SingleRangeData> aCacheData;