[Bash 4.4.5] Variable indirection, error on empty variable

[Otenba]

Machine: x86_64

OS: linux-gnu

Compiler: gcc

Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-unknown-linux-gnu' -DCONF_VENDOR='unknown' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_FORTIFY_SOURCE=2 -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -DDEFAULT_PATH_VALUE='/usr/local/sbin:/usr/local/bin:/usr/bin' -DSTANDARD_UTILS_PATH='/usr/bin' -DSYS_BASHRC='/etc/bash.bashrc' -DSYS_BASH_LOGOUT='/etc/bash.bash_logout' -Wno-parentheses -Wno-format-security

Machine Type: x86_64-unknown-linux-gnu

Bash Version: 4.4

Patch Level: 5

Release Status: release

Description:

Performing variable indirection using an empty value causes an error. It didn't in Bash 4.3.

Repeat-By:

$ reference=1

$ echo ${!indirect} #variable indirection using an unset variable

$ indirect=reference

$ echo ${!indirect} #variable indirection to a variable name

1

$ indirect=

$ echo ${!indirect} #variable indirection using an empty variable

-bash: : bad substitution

The expected behavior is that the result of an indirection be the same whether the indirect variable is empty or unset.