Tool settings for sequencer were not initialized, which caused crash
when adding strips.
There was fix for same issue in versioning rB0f81dafe6cec, but
subversion was not bumped, so files with uninitialized tool settings
may still exist.
Add `SEQ_tool_settings_get()` accessor function that will initialize
tool settings if they are missing. Change operator code to use
`SEQ_tool_settings_fit_method_get()` function instead of accessing
tool settings directly
Reviewed By: campbellbarton
Differential Revision: https://developer.blender.org/D11383
0f7becece7