valgrind: logic for last-ditch svg detection is busted

bIsGZip was never set, and the condition that uses it is additionally inverted

Change-Id: I0496bb27435c4323d74c1b99467d3ede68e7bee6

vcl/source/filter/graphicfilter.cxx

@@ -662,6 +662,8 @@ static bool ImpPeekGraphicFormat( SvStream& rStream, OUString& rFormatExtension,
             nCheckSize = nDecompressedSize < 256 ? nDecompressedSize : 256;
             aCodec.EndCompression();
             pCheckArray = sExtendedOrDecompressedFirstBytes;
+
+            bIsGZip = true;
         }
 
         bool bIsSvg(false);
@@ -696,7 +698,7 @@ static bool ImpPeekGraphicFormat( SvStream& rStream, OUString& rFormatExtension,
 
             pCheckArray = sExtendedOrDecompressedFirstBytes;
 
-            if(!bIsGZip)
+            if (bIsGZip)
             {
                 nCheckSize = nDecompressedSize < 2048 ? nDecompressedSize : 2048;
             }