[BUG] drop collection and REBUILD corrupts the file

[nant1086]

Version: litedb-ce-v5.0.7 / LiteDB Studio 1.0.2.0 / Windows 10 / Net Core 3

Describe the bug
First of all, I think this project is amazing!, after some toying with it, I found a scenario which throws an error and I wasn't able to access the database anymore

Steps to reproduce

1. Open the file with ConnectionType.Shared,
2. Insert rows to 1 single collection, there is one single collection only
3. With LiteDB Studio, execute drop collection then rebuild with collation or selecting the rebuild word only
4. Try to connect to the file and this error is thrown: Unable to cast object of type 'LiteDB.Engine.HeaderPage' to type 'LiteDB.Engine.IndexPage'.

A possible workaround is to delete all rows instead of dropping the collection, then rebuild to reduce the file size, and everything works ok

I hope this bug isn't so hard to solve, good luck!

[lbnascimento]

@nant1086 This issue has been fixed in the master and its fix will be present in the next incremental release.