Your installation of Gramps should include an example family tree database. This is used to provide a known stable environment for testing.
If you think you have a bug in your database, try the same operation with the example family tree. If the problem happens there as well, then it is probably not due to a corruption in your data.
Follow these steps to load the example family tree.
1. Find example.gramps.gz on your system. For example, /usr/share/doc/gramps/example/gramps/
2. Open example.gramps.gz, and extract example.gramps to a temporary location.
3. Start Gramps
4. Create a new family tree. Give it some name, such as example
5. Open this new family tree. It will be empty.
6. In Edit > Preferences, set the media path. This could be in a new directory, to keep it separate to your own family tree media. (eg ~/gramps/example/)
7. Copy the media files from the example directory (that you found in step 1, above) to this media path directory.
8. In Gramps, use File > Import to import example.gramps.