processMergedCells wants col count not row count

lib/importer/sheets.js

@@ -106,7 +106,7 @@ function processMergedCells(wantedColumns, preview) {
 // Given a session and a sheet name, gets a preview of the data held there
 // returning either a 2dim array of rows/cells or null if that specific sheet
 // is empty.
-exports.GetPreview = (session, sheet) => {
+exports.GetPreview = (session, sheet, count=10) => {
   const dimensions = backend
         .SessionGetInputDimensions(session.backendSid)
         .sheetDimensions.get(sheet);
@@ -115,7 +115,7 @@ exports.GetPreview = (session, sheet) => {
     sheet: sheet,
     start: {row: 0, column: 0},
     end: {row: dimensions.rows, column: dimensions.columns > 0 ? dimensions.columns - 1 : 0 }
-  }, Math.min(10, dimensions.rows), 0, 0)[0];
+  }, Math.min(count, dimensions.rows), 0, 0)[0];
 
   // TODO: Is there a better way to tell if the sheet is empty than iterating
   // all the cells? - we should have something in SessionGetInputDimensions
@@ -131,7 +131,7 @@ exports.GetPreview = (session, sheet) => {
     return null;
   }
 
-  return processMergedCells(Math.min(10, dimensions.rows), preview);
+  return processMergedCells(dimensions.columns, preview);
 };