fix reused variable in check_file_diff_approvals (#34387)

tools/check_file_diff_approvals.sh

@@ -265,6 +265,7 @@ fi
 
 OP_FILE_CHANGED=`git diff --name-only --diff-filter=AMR upstream/$BRANCH |grep -oE ".+_op..*" || true`
 if [ "${OP_FILE_CHANGED}" != "" ] && [ "${GIT_PR_ID}" != "" ]; then
+    ERROR_LINES=""
     for OP_FILE in ${OP_FILE_CHANGED};
     do
         CHECK_OBJECT_FLAGS=`git diff -U0 upstream/$BRANCH ${PADDLE_ROOT}/${OP_FILE} |grep "+" |grep -E "ShareDataWith[(]|ShareBufferWith[(]" || true`
@@ -295,6 +296,7 @@ fi
 
 UNITTEST_FILE_CHANGED=`git diff --name-only --diff-filter=AM upstream/$BRANCH |grep -E "test_.*.\.py" || true`
 if [ "${UNITTEST_FILE_CHANGED}" != "" ] && [ "${GIT_PR_ID}" != "" ]; then
+    ERROR_LINES=""
     for TEST_FILE in ${UNITTEST_FILE_CHANGED};
     do
         HAS_SKIP_CHECK_GRAD_CI=`git diff -U0 upstream/$BRANCH ${PADDLE_ROOT}/${TEST_FILE} |grep "@skip_check_grad_ci" || true`