lib/preview: `shfmt` && `shellcheck`

Fix theme file path globbing when $BASH_IT contains any spaces.

My apologies to future `git blame` hunters ♥

clean_files.txt

@@ -80,6 +80,7 @@ completion/available/wpscan.completion.bash
 # libraries
 lib/helpers.bash
 lib/log.bash
+lib/preview.bash
 lib/search.bash
 lib/utilities.bash
 

lib/preview.bash

@@ -1,5 +1,8 @@
-if [[ "${BASH_PREVIEW:-}" ]];
+# shellcheck shell=bash
-then
+#
+# Displays the prompt from each _Bash It_ theme.
+
+if [[ -n "${BASH_PREVIEW:-}" ]]; then
 	unset BASH_PREVIEW #Prevent infinite looping
 	echo "
 
@@ -7,13 +10,11 @@ then
 
   "
 
-  THEMES="$BASH_IT/themes/*/*.theme.bash"
+	for theme in "${BASH_IT?}/themes"/*/*.theme.bash; do
-  for theme in $THEMES
-  do
 		BASH_IT_THEME=${theme%.theme.bash}
 		BASH_IT_THEME=${BASH_IT_THEME##*/}
 		echo "
     $BASH_IT_THEME"
-    echo "" | bash --init-file "${BASH_IT}/bash_it.sh" -i
+		echo "" | bash --init-file "${BASH_IT?}/bash_it.sh" -i
 	done
 fi