feat: Use state helper for base image reads (#1839)

src/install.sh

@@ -11,17 +11,11 @@ backup () {
   local iso="$1"
   local name="unknown"
   local root="$STORAGE/backups"
-  local previous="$STORAGE/windows.base"
-
-  if [ -f "$previous" ]; then
-
-    previous=$(<"$previous")
-    previous="${previous//[![:print:]]/}"
+  local previous
 
+  previous=$(readState "base") || return 1
   [ -n "$previous" ] && name="${previous%.*}"
 
-  fi
-
   if ! makeDir "$root"; then
     error "Failed to create directory \"$root\" !"
     return 1
@@ -59,12 +53,9 @@ skipInstall() {
   local method=""
   local magic byte
   local boot="$STORAGE/windows.boot"
-  local previous="$STORAGE/windows.base"
+  local previous
 
-  if [ -f "$previous" ]; then
-
-    previous=$(<"$previous")
-    previous="${previous//[![:print:]]/}"
+  previous=$(readState "base") || return 1
 
   if [ -n "$previous" ]; then
     if [[ "${STORAGE,,}/${previous,,}" != "${iso,,}" ]]; then
@@ -100,8 +91,6 @@ skipInstall() {
     fi
   fi
 
-  fi
-
   [ -f "$boot" ] && hasDisk && return 0
 
   [ ! -f "$iso" ] && return 1