bash-completion: fix few bash set -u issues

This is the same fix as in reference commit, and the same reason.  Just
correct few files missed earlier.

Reference: abbcec4fc9
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

bash-completion/chcpu

@@ -12,7 +12,7 @@ _chcpu_module()
 			CPULIST_ALL=$(sed 's/^/{/; s/-/../g; s/,/} {/g; s/$/}/' /sys/devices/system/cpu/offline)
 			for WORD in $(eval echo $CPULIST_ALL); do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					CPULIST="$WORD $CPULIST"
+					CPULIST="$WORD ${CPULIST:-""}"
 				fi
 			done
 			compopt -o nospace
@@ -26,7 +26,7 @@ _chcpu_module()
 			CPULIST_ALL=$(sed 's/^/{/; s/-/../g; s/,/} {/g; s/$/}/' /sys/devices/system/cpu/online)
 			for WORD in $(eval echo $CPULIST_ALL); do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					CPULIST="$WORD $CPULIST"
+					CPULIST="$WORD ${CPULIST:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/lsblk

@@ -20,15 +20,15 @@ _lsblk_module()
 			prefix="${cur%$realcur}"
 			for I in /sys/dev/block/*; do
 				J=${I##*/}
-				MAJOR_ALL="$MAJOR_ALL ${J%%:*}"
+				MAJOR_ALL="${MAJOR_ALL:-""} ${J%%:*}"
 			done
-			for WORD in $MAJOR_ALL; do
+			for WORD in ${MAJOR_ALL:-""}; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					MAJOR="$WORD $MAJOR"
+					MAJOR="$WORD ${MAJOR:-""}"
 				fi
 			done
 			compopt -o nospace
-			COMPREPLY=( $(compgen -P "$prefix" -W "$MAJOR" -S ',' -- $realcur) )
+			COMPREPLY=( $(compgen -P "$prefix" -W "${MAJOR:-""}" -S ',' -- $realcur) )
 			return 0
 			;;
 		'-o'|'--output')
@@ -37,7 +37,7 @@ _lsblk_module()
 			prefix="${cur%$realcur}"
 			for WORD in $LSBLK_COLS_ALL; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					LSBLK_COLS="$WORD $LSBLK_COLS"
+					LSBLK_COLS="$WORD ${LSBLK_COLS:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/lscpu

@@ -15,7 +15,7 @@ _lscpu_module()
 				CONFIGURED ONLINE MAXMHZ MINMHZ"
 			for WORD in $OPTS_ALL; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					OPTS="$WORD $OPTS"
+					OPTS="$WORD ${OPTS:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/lslogins

@@ -35,7 +35,7 @@ _lslogins_module()
 			prefix="${cur%$realcur}"
 			for WORD in $LSLOGINS_COLS_ALL; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					LSLOGINS_COLS="$WORD $LSLOGINS_COLS"
+					LSLOGINS_COLS="$WORD ${LSLOGINS_COLS:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/lsns

@@ -14,7 +14,7 @@ _lsns_module()
 			prefix="${cur%$realcur}"
 			for WORD in $LSNS_COLS_ALL; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					LSNS_COLS="$WORD $LSNS_COLS"
+					LSNS_COLS="$WORD ${LSNS_COLS:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/mount

@@ -15,7 +15,7 @@ _mount_module()
 			prefix="${cur%$realcur}"
 			for WORD in $TYPES; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					TYPE_COLS="$WORD $TYPE_COLS"
+					TYPE_COLS="$WORD ${TYPE_COLS:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/setpriv

@@ -38,7 +38,7 @@ _setpriv_module()
 			GIDS_ALL=$(getent group | awk -F: '{print $3}')
 			for WORD in $GIDS_ALL; do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					GIDS="$WORD $GIDS"
+					GIDS="$WORD ${GIDS:-""}"
 				fi
 			done
 			compopt -o nospace

bash-completion/taskset

@@ -12,7 +12,7 @@ _taskset_module()
 			CPULIST_ALL=$(sed 's/^/{/; s/-/../g; s/,/} {/g; s/$/}/' /sys/devices/system/cpu/online)
 			for WORD in $(eval echo $CPULIST_ALL); do
 				if ! [[ $prefix == *"$WORD"* ]]; then
-					CPULIST="$WORD $CPULIST"
+					CPULIST="$WORD ${CPULIST:-""}"
 				fi
 			done
 			compopt -o nospace