fixed bad SourceNode X SourceNode join in HTTP model

Author: erik-krogh

javascript/ql/src/semmle/javascript/frameworks/Express.qll

@@ -688,8 +688,7 @@ module Express {
     override RouteHandler getRouteHandler() { result = rh }
 
     override Expr getNameExpr() {
-      exists(DataFlow::PropWrite write |
-        getAHeaderSource().flowsTo(write.getBase()) and
+      exists(DataFlow::PropWrite write | getAHeaderSource().getAPropertyWrite() = write |
         result = write.getPropertyNameExpr()
       )
     }

javascript/ql/src/semmle/javascript/frameworks/Fastify.qll

@@ -283,8 +283,7 @@ module Fastify {
     override RouteHandler getRouteHandler() { result = rh }
 
     override Expr getNameExpr() {
-      exists(DataFlow::PropWrite write |
-        this.getAHeaderSource().flowsTo(write.getBase()) and
+      exists(DataFlow::PropWrite write | getAHeaderSource().getAPropertyWrite() = write |
         result = write.getPropertyNameExpr()
       )
     }