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

In that case, updating is obviously not possible.

UPDATE AND START SERVER.bat

@@ -2,24 +2,27 @@
 
 echo Updating SpaceNinjaServer...
 git fetch --prune
-git stash
-git checkout -f origin/main
+if %errorlevel% == 0 (
+	git stash
+	git checkout -f origin/main
 
-if exist static\data\0\ (
+	if exist static\data\0\ (
 		echo Updating stripped assets...
 		cd static\data\0\
 		git pull
 		cd ..\..\..\
-)
+	)
 
-echo Updating dependencies...
-call npm i --omit=dev
+	echo Updating dependencies...
+	call npm i --omit=dev
 
-call npm run build
-if %errorlevel% == 0 (
+	call npm run build
+	if %errorlevel% == 0 (
 		call npm run start
 		echo SpaceNinjaServer seems to have crashed.
+	)
 )
+
 :a
 pause > nul
 goto a

UPDATE AND START SERVER.sh

@@ -2,22 +2,23 @@
 
 echo "Updating SpaceNinjaServer..."
 git fetch --prune
-git stash
-git checkout -f origin/main
+if [ $? -eq 0 ]; then
+    git stash
+    git checkout -f origin/main
 
-if [ -d "static/data/0/" ]; then
+    if [ -d "static/data/0/" ]; then
         echo "Updating stripped assets..."
         cd static/data/0/
         git pull
         cd ../../../
-fi
+    fi
 
-echo "Updating dependencies..."
-npm i --omit=dev
+    echo "Updating dependencies..."
+    npm i --omit=dev
 
-npm run build
-if [ $? -eq 0 ]; then
+    npm run build
+    if [ $? -eq 0 ]; then
         npm run start
         echo "SpaceNinjaServer seems to have crashed."
+    fi
 fi
-