Value for capability "webSocketUrl" cannot be false in the "new session algorithm" (#725)

Author: whimboo

index.bs

@@ -1171,7 +1171,7 @@ with parameters |session|, |capabilities|, and |flags| is:
 1. Let |webSocketUrl| be the result of [=getting a property=] named
    "<code>webSocketUrl</code>" from |capabilities|.
 
-1. If |webSocketUrl| is undefined or false, return.
+1. If |webSocketUrl| is undefined, return.
 
 1. [=Assert=]: |webSocketUrl| is true.