prevent possible NPE in shell tab completion

bindings/java/src/net/hyperic/sigar/cmd/PTQL.java

@@ -58,12 +58,12 @@ public class PTQL
         String attr = line.substring(ix+1, line.length());
 
         Method method = (Method)this.methods.get(attrClass);
-        Class subtype = method.getReturnType();
-
         if (method == null) {
             return line;
         }
 
+        Class subtype = method.getReturnType();
+
         boolean isSigarClass = ProcessQueryBuilder.isSigarClass(subtype);
 
         int ix2 = attr.indexOf(".");