fix grep version from isolationtester

Author: Aleksandr Kozhemyakin

tests_install/make_installcheck.sh

@@ -148,8 +148,8 @@ done <<< "$opts";
 # Workaround for incorrect libpq in isolationtester for v14 on altlinux. (PGPRO-5369)
 ldlib=""
 if grep 'CPE_NAME="cpe:/o:alt:.*:p10"\|ALT Server 9.0\|ALT 8 SP Server' /etc/*-release >/dev/null 2>&1; then
-    ver=`$1/bin/pg_config --version | grep -oP '\d{2}'`
-    if [ $ver == 14 ]; then
+    ver=`$1/bin/pg_config --version | sed -nE "s/[^0-9]+([0-9]+).*/\1/p"`
+    if [[ ! -z $ver && $ver == 14 ]]; then
         ldlib="LD_LIBRARY_PATH=$1/lib:$LD_LIBRARY_PATH"
     fi
 fi