WaE: use of unary operator that may be intended as compound assignment

Change-Id: Ib1718e5d3a0f7f1e4d1941674743900be12d4e1f

filter/source/msfilter/msdffimp.cxx

@@ -2766,7 +2766,7 @@ void DffPropertyReader::ImportGradientColor( SfxItemSet& aSet,MSO_FillType eMSO_
         nChgColors ^= 1;
     else if ( nFocus < 0 )//If it is a negative focus, the color will be swapped
     {
-        nFocus =- nFocus;
+        nFocus = -nFocus;
         nChgColors ^= 1;
     }