""for empty string.
array=(=one = two)
You have an array element on the form
[index]=. The shell will interpret this as an independent element with index
index and value
This may happen as part of the expression
[index]= value, where the space is not allowed and causes the shell to interpret it as
If you wanted the element to have a value, remove the spaces after
If you wanted to assign an empty string, explicitly use empty quotes:
[index]="". This makes no difference to the shell, but will make your intention clear to shellcheck and other humans.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.