Panic when querying dolt_diff after updating a text field

[fulghum]

When a text field in a row has been updated, Doltgres panics when querying the diff.

create table employees(id int8, first_name text, last_name text, primary key(id));
insert into employees values(1, 'John', 'Smith');
call dolt_commit('-Am', 'creating table on main');
call dolt_checkout('-b', 'branch1');
update employees set first_name='' where id=1;
select * from dolt_diff('main', 'WORKING', 'employees');

The steps above cause a panic with this stack trace:

panic: runtime error: slice bounds out of range [:203855527] with capacity 92

goroutine 434 [running]:
github.com/dolthub/doltgresql/utils.UnsafeAdvanceReader(...)
        /Users/jason/Projects/doltgresql/utils/reader.go:364
github.com/dolthub/doltgresql/server/types.serializedStringCompare({0x140029eb7a4?, 0x140029eb7a4?, 0x2c?}, {0x14001febfa4?, 0x14001febfa4?, 0x2c?})
        /Users/jason/Projects/doltgresql/server/types/text.go:267 +0x140
github.com/dolthub/doltgresql/server/types.TextType.SerializedCompare({}, {0x140029eb7a4?, 0x10389aa6c?, 0x1064ba918?}, {0x14001febfa4?, 0x1400360d4a0?, 0x1400360d500?})
        /Users/jason/Projects/doltgresql/server/types/text.go:181 +0x70
github.com/dolthub/dolt/go/store/val.ExtendedTupleComparator.CompareValues({{0x1064c4020, 0x1096f5820}, {0x140035e77c0, 0x2, 0x2}}, 0x106243280?, {0x140029eb7a4?, 0x94?, 0x14004580c98?}, {0x14001febfa4?, ...}, ...)
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/store/val/extended_comparator.go:52 +0xb4
github.com/dolthub/dolt/go/store/val.ExtendedTupleComparator.Compare({{0x1064c4020, 0x1096f5820}, {0x140035e77c0, 0x2, 0x2}}, {0x140029eb7a4, 0x2c, 0x5c}, {0x14001febfa4, 0x2c, ...}, ...)
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/store/val/extended_comparator.go:40 +0x28c
github.com/dolthub/dolt/go/store/val.TupleDesc.Compare({{0x14004607688, 0x2, 0x4}, {0x140035e77c0, 0x2, 0x2}, {0x1064c4060, 0x1400124cdb0}, {0x14004607698, 0x0, ...}}, ...)
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/store/val/tuple_descriptor.go:160 +0x98
github.com/dolthub/dolt/go/store/prolly.DiffMaps.makeDiffCallBack.func1({0x1064ba918, 0x14003417040}, {{0x140029eb7dc, 0xa, 0x24}, {0x140029eb7a4, 0x2c, 0x5c}, {0x14001febfa4, 0x2c, ...}, ...})
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/store/prolly/tuple_map.go:162 +0xc0
github.com/dolthub/dolt/go/store/prolly/tree.DiffOrderedTrees[...]({_, _}, {{{0x88, 0xa, 0x80, 0x4, 0x0}, {0x50, 0x2c, 0x48, ...}, ...}, ...}, ...)
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/store/prolly/tree/map.go:60 +0x280
github.com/dolthub/dolt/go/store/prolly.DiffMaps({_, _}, {{{{0x88, 0xa, 0x80, 0x4, 0x0}, {0x50, 0x2c, 0x48, ...}, ...}, ...}, ...}, ...)
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/store/prolly/tuple_map.go:115 +0x11c
github.com/dolthub/dolt/go/libraries/doltcore/sqle/dtables.prollyDiffIter.queueRows({{{{{...}, {...}, 0x1, 0x0, 0x0, {...}}, {0x1064cb970, 0x14001dc0000}, {{...}, {...}, ...}}, ...}, ...}, ...)
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/libraries/doltcore/sqle/dtables/diff_iter.go:337 +0x88
github.com/dolthub/dolt/go/libraries/doltcore/sqle/dtables.newProllyDiffIter.func1()
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/libraries/doltcore/sqle/dtables/diff_iter.go:309 +0x48
created by github.com/dolthub/dolt/go/libraries/doltcore/sqle/dtables.newProllyDiffIter in goroutine 383
        /Users/jason/go/pkg/mod/github.com/dolthub/dolt/[email protected]/libraries/doltcore/sqle/dtables/diff_iter.go:308