(core) Avoid an error when pasting data with first row shorter than the rest

Summary:
Pasting data like `A\nB\tC` was failing because the first row, used for
checking column type (to handle rich data), was failing on an undefined value.

Discovered while trying out the fix in https://phab.getgrist.com/D3110.

Test Plan: Tested manually. The case mentioned now works as expected.

Reviewers: alexmojaki

Reviewed By: alexmojaki

Differential Revision: https://phab.getgrist.com/D3111

app/client/components/BaseView.js

@@ -373,7 +373,7 @@ BaseView.prototype._parsePasteForView = function(data, fields) {
     if (!col.length) {
       return col;
     }
-    const typeMatches = col[0].colType === updateColTypes[idx];
+    const typeMatches = col[0] && col[0].colType === updateColTypes[idx];
     const parser = parsers[idx];
     return col.map(v => {
       if (v) {