Today Aseprite v1.2.3 is available with some bug fixes:

• New Edit > Adjustments > Brightness/Contrast menu option
• New Layer > Lock Layers menu option
• Restored default behavior on “Add to selection”
• Fixed Switch Colors and Eyedropper behavior when the Edit palette mode is enabled
• Fixed crash using negative numbers in Despeckle filter
• Fixed problem inserting a digit/character in a text field with one digit/character
• Fixed “Paint Brush” mode for custom brushes
• macOS: Fixed Left/Right keys to move the selection
• macOS: Fixed native file selector (don’t show it again if we swich to another window with ⌘Tab

More info in the blog