Bug 633055: Make Bug.legal_values explicitly throw an error if you pass "undef"

for the "field" parameter
r=dkl, a=mkanat


git-svn-id: svn://10.0.0.236/trunk@261939 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/webtools/bugzilla/Bugzilla/WebService/Bug.pm

@@ -569,6 +569,10 @@ sub create {
 
 sub legal_values {
     my ($self, $params) = @_;
+
+    defined $params->{field} 
+        or ThrowCodeError('param_required', { param => 'field' });
+
     my $field = Bugzilla::Bug::FIELD_MAP->{$params->{field}} 
                 || $params->{field};