don't access deleted cells

This copy&pasted code that got fixed in 2926c9e4, so fix it as well.

Change-Id: I0a038b57a428640dae8cdf17f33a2eab50b0187c
Reviewed-on: https://gerrit.libreoffice.org/63177
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

sc/source/core/data/formulacell.cxx

@@ -4327,6 +4327,8 @@ struct ScDependantsCalculator
             case svSingleRef:
                 {
                     ScSingleRefData aRef = *p->GetSingleRef(); // =Sheet1!A1
+                    if( aRef.IsDeleted())
+                        return false;
                     ScAddress aRefPos = aRef.toAbs(mrPos);
 
                     if (!mrDoc.TableExists(aRefPos.Tab()))
@@ -4361,6 +4363,8 @@ struct ScDependantsCalculator
             case svDoubleRef:
                 {
                     ScComplexRefData aRef = *p->GetDoubleRef();
+                    if( aRef.IsDeleted())
+                        return false;
                     ScRange aAbs = aRef.toAbs(mrPos);
 
                     // Multiple sheet