v1.6.3

### Release Notes

This is a bugfix release that fixes a rare problem causing novelWriter to crash if the spell checker language setting was configured to an empty value.

A few other minor issues have also been fixed: The project language setting is now properly exported to ODT documents. Spaces are no longer inserted automatically in front of colons in certain meta data settings when the feature is enabled (it is primarily used for French). Lastly, the slider splitting the editor and viewer panels can no longer be dragged until the viewer disappears. It was not necessarily obvious how the viewer panel could be restored in such cases.

### Detailed Changelog

**Bugfixes**

* Fixed an issue where the project language setting was not exported when building Open Document files. Issue #1073. PR #1087.
* Fixed an issue where the splitter in the main window could be dragged until it hid the document viewer panel. This is no longer possible. Issue #1085. PR #1087.
* Fixed an issue where an empty spell check language setting would crash novelWriter. Issue #1096. PR #1098.
* Added a checker that blocks the automatic insertion of spaces in front of special characters in the cases where the character is a colon in either a meta tag, or as part of the synopsis keyword. This feature is used for certain languages like French and Spanish. Issue #1090. PR #1099.