corrected string comparison, always use quotes

#24
https://unix.stackexchange.com/questions/131766/why-does-my-shell-script-choke-on-whitespace-or-other-special-characters

the linked issue failure corner case was when the output of command contained glob characters, for ex: `a[2]`
if string is unquoted on RHS of comparison operator, it is treated as glob comparison, not string comparison
hence why quotes are needed here

Author: learnbyexample

exercises/GNU_grep/solve

@@ -43,7 +43,7 @@ while IFS= read -u3 -r ref_line && read -u4 -r sol_line; do
             sub_sol=0
         fi
 
-        if [[ $(eval "command ${ref_line:10}") == $(eval "command $sol_line") ]]; then
+        if [[ "$(eval "command ${ref_line:10}")" == "$(eval "command $sol_line")" ]]; then
             (( sol_count++ ))
             # use color if terminal supports
             echo '---------------------------------------------'