refactor(installer): add an additional check to env removal in case an invalid external variable was set

https://github.com/dw-0/kiauh/issues/488

scripts/KlipperScreen-install.sh

@@ -115,18 +115,24 @@ check_requirements()
 
 create_virtualenv()
 {
-    if [ -d $KSENV ]; then
+    if [ "${KSENV}" = "/" ]; then
+        echo_error "Failed to resolve venv location. Aborting."
+        exit 1
+    fi
+
+    if [ -d "$KSENV" ]; then
         echo_text "Removing old virtual environment"
-        rm -rf ${KSENV}
+        rm -rf "${KSENV}"
     fi
     
     echo_text "Creating virtual environment"
-    python3 -m venv ${KSENV}
+    python3 -m venv "${KSENV}"
 
-    if ! source ${KSENV}/bin/activate; then
+    if ! . "${KSENV}/bin/activate"; then
         echo_error "Could not activate the enviroment, try deleting ${KSENV} and retry"
         exit 1
     fi
+
     if [[ "$(uname -m)" =~ armv[67]l ]]; then
         echo_text "Using armv[67]l! Adding piwheels.org as extra index..."
         pip --disable-pip-version-check install --extra-index-url https://www.piwheels.org/simple -r ${KSPATH}/scripts/KlipperScreen-requirements.txt
@@ -152,7 +158,7 @@ create_virtualenv()
         fi
     fi
     deactivate
-    echo_ok "Virtual enviroment created"
+    echo_ok "Virtual environment created"
 }
 
 install_systemd_service()