Once scaled, Silva Images cannot have scaling removed

[Kit Blake]

When an image is uploaded it sometimes needs to be scaled. An Author can scale with various means (100x200, 100x*, *x200, 40%), but once an image is scaled the scaling can never be removed. If the value is removed, the form then errors with the feedback:
"'' is not a valid scale identifier. Probably a x percent symbol is missing."

There is a workaround, but most Authors won't think of it.

[Wim Boucquaert (wim-boucquaert)]

Added text "Use 100% to scale back to the orginal format." to make it more clear

[Kit Blake (kitblake)]

Could you change the string to to "Enter 100% to return to the original format." in place of "Use 100% to scale back to the orginal format."?
Note the typo in the original 'orginal'.
We don't scale it down and then back, that would steadily reduce quality.

[Emiliano D'Alterio (emidal)]

This is fixed. Now if the user leaves the field empty or inputs an invalid size, the image will be automatically sized to the default 100%.