/setblock property value suggestions do not tab-complete correctly.

When use setblock and setting properties on the new block, pressing "tab" to suggest property values does not complete correctly.

For instance, enter the following command

/setblock ~ ~5 ~ minecraft:anvil[facing= 

A list of possible values will be presented above the cursor:

east
north
south
west

Next to the cursor the first value will appear in gray color, 'east', and in the list of suggestions, 'east' is highlighted yellow:

Now, type the letter 'n'. We expect the suggestion to change to 'north' (as with many other contextual command suggestions). Instead, 'east' will remain highlighted yellow. Pressing tab now entirely replaces the current property value with 'east' instead of completing 'n...' to 'north'.