*Steps to reproduce:*
# Open a Unity Project
# Import TMP Essential Resources via Window > TextMeshPro > Import TMP Essential Resources
# Open the Sprite Importer via Window > TextMeshPro > Sprite Importer
# Select any valid asset for the Sprite Texture Atlas property
# Set 'Sprite Data Source' as a common but invalid file type (e.g. a .cs or .txt file)
# Click 'Create Sprite Asset'
# Observe how a 'The Sprite Data Source file appears to be invalid or incorrectly formatted' message is written to the Sprite Importer window
# Set 'Sprite Data Source' as an uncommon but still invalid file type (e.g. a .cginc file like TMPro.cginc)
# Click 'Create Sprite Asset' 

*Actual results:* Nothing happens. No 'invalid of incorrectly formatted' message is written to the Window even though the file type is still an invalid one. It appears as if the button is doing nothing.

*Expected results:* The Sprite Importer Window writes a 'The Sprite Data Source file appears to be invalid or incorrectly formatted' message for all invalid file types, even if they aren't common ones like .cs or .txt.

*Reproducible with versions:* 6000.1.0a4, 6000.0.27f1, 2022.3.52f1, 2021.3.46f1

*Not reproducible with versions:* - 

*Can’t test with versions:* - 

*Tested on (OS):* Windows 11

*Notes:* -