Slightly more robust test

tests/cases/XML/feed-rss0.yaml

@@ -28,7 +28,7 @@ Minimal feed without channel 2:
 Feed language 1: # demonstrate walking up the DOM
     input: >
         <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://channel.netscape.com/rdf/simple/0.9/" xml:lang="fr">
-            <channel xml:lang=""/>
+            <channel xml:lang=" "/>
         </rdf:RDF>
     output:
         format: rdf
@@ -37,7 +37,7 @@ Feed language 1: # demonstrate walking up the DOM
 
 Feed language 2: # demonstrate walking up the DOM
     input: >
-        <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://channel.netscape.com/rdf/simple/0.9/" xml:lang="">
+        <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://channel.netscape.com/rdf/simple/0.9/" xml:lang=" ">
             <channel xml:lang="fr"/>
         </rdf:RDF>
     output: