chore: abort update and start scripts when .git folder is missing

In that case, updating is obviously not possible.

UPDATE AND START SERVER.bat

@@ -2,6 +2,7 @@
 
 echo Updating SpaceNinjaServer...
 git fetch --prune
+if %errorlevel% == 0 (
 	git stash
 	git checkout -f origin/main
 
@@ -20,6 +21,8 @@ if %errorlevel% == 0 (
 		call npm run start
 		echo SpaceNinjaServer seems to have crashed.
 	)
+)
+
 :a
 pause > nul
 goto a

UPDATE AND START SERVER.sh

@@ -2,6 +2,7 @@
 
 echo "Updating SpaceNinjaServer..."
 git fetch --prune
+if [ $? -eq 0 ]; then
     git stash
     git checkout -f origin/main
 
@@ -20,4 +21,4 @@ if [ $? -eq 0 ]; then
         npm run start
         echo "SpaceNinjaServer seems to have crashed."
     fi
-
+fi