ShrinkRefTokenToDataRange:operator(): check if it's really ScDoubleRefToken

Resolved scary "ScToken::GetDoubleRef: virtual dummy called" debug message.

sc/source/ui/unoobj/chart2uno.cxx

@@ -1395,6 +1395,11 @@ public:
         if (ScRefTokenHelper::isExternalRef(rRef))
             return;
 
+        // Don't assume an ScDoubleRefToken if it isn't. It can be at least an
+        // ScSingleRefToken, then there isn't anything to shrink.
+        if (rRef->GetType() != svDoubleRef)
+            return;
+
         ScComplexRefData& rData = rRef->GetDoubleRef();
         ScSingleRefData& s = rData.Ref1;
         ScSingleRefData& e = rData.Ref2;