util: fix leak in setstyle (Coverity #50151+#50152)

As pointed by Coverity, there are a few cases where the list of the keys
of a dictionary is being requested, but at the end the array that was
created to hold these keys was not freed.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

util/setstyle.c

@@ -203,6 +203,7 @@ static void hackPaths(WMPropList * style, const char *prefix)
 		}
 	}
 
+	WMReleasePropList(keys);
 }
 
 static WMPropList *getColor(WMPropList * texture)
@@ -313,6 +314,7 @@ static void hackStyle(WMPropList * style)
 			}
 		}
 	}
+	WMReleasePropList(keys);
 
 	if (!foundIconTitle) {
 		/* set the default values */