cid#1697494: silence Overflowed constant

Change-Id: I678b844b9904015602cbcdab3bfbd7176ae3d0c0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/210281
Tested-by: Jenkins
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>

drawinglayer/source/tools/emfphelperdata.cxx

@@ -1568,8 +1568,6 @@ namespace emfplushelper
 
             rMS.ReadUInt16(type).ReadUInt16(flags).ReadUInt32(size).ReadUInt32(dataSize);
 
-            sal_uInt64 next = rMS.Tell() + (size - 12);
-
             if (size < 12)
             {
                 SAL_WARN("drawinglayer.emf", "Size field is less than 12 bytes");
@@ -1581,6 +1579,8 @@ namespace emfplushelper
                 break;
             }
 
+            sal_uInt64 next = rMS.Tell() + (size - 12);
+
             if (dataSize > (size - 12))
             {
                 SAL_WARN("drawinglayer.emf", "DataSize field is greater than Size-12");