update doc on getExceptionalNode

Author: erik-krogh

javascript/ql/src/semmle/javascript/Expr.qll

@@ -247,8 +247,8 @@ class Expr extends @expr, ExprOrStmt, ExprOrType, AST::ValueNode {
   }
 
   /**
-   * Gets the data-flow node where exceptional data-flow will flow if this expression
-   * causes an exception to be thrown.
+   * Gets the data-flow node where exceptions thrown by this expression will
+   * propagate if this expression causes an exception to be thrown.
    */
   DataFlow::Node getExceptionalNode() {
     if exists(this.getEnclosingStmt().getEnclosingTryCatchStmt())