[Gui] remove unnecessary Boolean comparisons

src/Gui/Thumbnail.cpp

@@ -73,7 +73,7 @@ unsigned int Thumbnail::getMemSize (void) const
 void Thumbnail::Save (Base::Writer &writer) const
 {
     // It's only possible to add extra information if force of XML is disabled
-    if (writer.isForceXML() == false)
+    if (!writer.isForceXML())
         writer.addFile("thumbnails/Thumbnail.png", this);
 }