[glom] ReportBuilder: Handle -1 column/row counts from DataModel.

[Murray Cumming <murrayc src gnome org>]

commit 303418c6974c9168683ac7cbc7f31b6abbe9fe98
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Mar 29 14:45:04 2016 +0200

    ReportBuilder: Handle -1 column/row counts from DataModel.

 glom/libglom/report_builder.cc |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/glom/libglom/report_builder.cc b/glom/libglom/report_builder.cc
index 657d292..b85f2fb 100644
--- a/glom/libglom/report_builder.cc
+++ b/glom/libglom/report_builder.cc
@@ -242,8 +242,8 @@ bool ReportBuilder::report_build_groupby(const FoundSet& found_set_parent, xmlpp
     }
     else
     {
-      const guint rows_count = datamodel->get_n_rows();
-      for(guint row = 0; row < rows_count; ++row)
+      const auto rows_count = datamodel->get_n_rows(); // -1 means unknown.
+      for(int row = 0; row < rows_count; ++row)
       {
         const auto group_value = datamodel->get_value_at(0 /* col*/, row); //TODO: Catch exceptions.
 
@@ -390,9 +390,9 @@ bool ReportBuilder::report_build_records(const FoundSet& found_set, xmlpp::Eleme
     }
     else
     {
-      const guint rows_count = datamodel->get_n_rows();
+      const auto rows_count = datamodel->get_n_rows();
 
-      for(guint row = 0; row < rows_count; ++row)
+      for(int row = 0; row < rows_count; ++row)
       {
         auto nodeRow = parent_node.add_child_element("row");