fix(color): UI issues adding and removing labels

[philmoz]

Fixes:

• adding a new label sets the new label as the filter selection hiding all models since none use the label
• removing a label when single select filter mode is enabled, and a label other than the one being removed is selected as the filter, will result in all models being shown, not just the ones that match the filter
• characters that are not allowed in labels are now removed before truncating new labels to the maximum length