X-Plane improve Navdata updates

x-plane/default.nix

@@ -141,6 +141,8 @@ let
     elif [ -e "$XPLANEPATH/Custom Data/cycle_info.txt" ]; then
         oldcycle=$(head -n1 "$XPLANEPATH/Custom Data/cycle_info.txt" | sed -E -n -e "s/^AIRAC cycle[ :]+([0-9]+)\r$/\1/p")
         [ -n "$oldcycle" ] || { printf "Unable to determine old AIRAC cycle\n" >&2; exit 1; }
+    else
+        oldcycle=
     fi
     f=$1
     [ -e "$f" ] || { printf "No such file or directory\n" >&2; exit 1; }
@@ -148,7 +150,9 @@ let
     cycle=''${cycle%.zip}
     newpath="$XPLANEPATH/Custom Data AIRAC$cycle"
 
-    if [ ! -h "$XPLANEPATH/Custom Data" ]; then
+    if [ -z "$oldcycle" ]; then
+        rm -r "$XPLANEPATH/Custom Data"
+    elif [ ! -h "$XPLANEPATH/Custom Data" ]; then
         mv "$XPLANEPATH/Custom Data" "$XPLANEPATH/Custom Data AIRAC$oldcycle"
     fi
 
@@ -173,7 +177,7 @@ let
     Also, you can place the FAACIFP18 file here, which you can get from the FAA website: https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/cifp/
     If the file FAACIFP18 is found in this folder, X-Plane will load instrument flight procedures from this file.
     EOF
-    rm "$XPLANEPATH/Custom Data"
+    rm -f "$XPLANEPATH/Custom Data"
     ln -sf "$newpath" "$XPLANEPATH/Custom Data"
   '';