No Tab indenting is not bad.
Just don't mix space and tab indenting in one block like you did in the screen shot.
Your error:
vel =
was indented with spaces and the next line(s) were indented with tabs.
Generally set your indenting in Editor->Preferences then "Text Editor->Indent".
Problems usually arise if you copy text from other sources which used the "other" editing and then edit it using your own preferences. Or if you use an exeternal editor with different indenting settings.