Signature parameter is calculated incorrectly for ENV and LABEL instructions

[rcjsuen]

If signature help is prompted for after the a character on the second line, the parameter that gets calculated is key2 instead of key. If the cursor is before or after the v then it is okay. If it is is after a or r then key2 gets returned.

FROM node
ENV var=\
value

If it is a LABEL instruction, the parameter calculation is completely off regardless of where the cursor is in the var word.

FROM node
LABEL var=\
value

Note however that the error cannot be reproduced with the following Dockerfiles.

FROM node
ENV var=\

FROM node
LABEL var=\