wrongly parsed equations

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here are some equations which aren't parse correctly

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$k{\cdot}\vec{a}$
gives an error
when I'm on k with the cursor: Empty expression detected. Please use the $...$ syntax.

When I'm at a different place: .../ascii.lua:3813: attempt to index local 'rightgrid' (a nil value)
notice that it works if I replace the {} around \cdot with spaces (or in this case with nothing)
(I got the {} so no space is needed when variable names (e.g. a) are used directly after it)

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$\mathbb{R}^2
gives an error when on \: Empty expression detected. Please use the $...$ syntax.

and otherwise it shows the wrong thing:

(not squared)

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thank you very much