Fixed bad_alloc in ErasureCodeShec

Makefile

@@ -36,6 +36,7 @@ all: ceph-config
 	patch -Np1 -d ceph-15.2.4 < ceph-15.2.4-fix_ceph-volume_systemd_unit.patch
 	patch -Np1 -d ceph-15.2.4 < ceph-15.2.4-no_git.patch
 	patch -Np1 -d ceph-15.2.4 < ceph-15.2.4-fix_librbd_duplicate.patch
+	patch -Np1 -d ceph-15.2.4 < ceph-15.2.4-fix_ErasureCodeShec.patch
 	if [ `uname -m` = 'armv7l' ] ; then \
 	    patch -Np1 -d ceph-15.2.4 < ceph-15.2.4-arm32_fix.patch ; \
 	fi

ceph-15.2.4-fix_ErasureCodeShec.patch

+diff -uNr ceph-15.2.4/src/erasure-code/shec/ErasureCodeShec.cc ceph-15.2.4-fix_ErasureCodeShec/src/erasure-code/shec/ErasureCodeShec.cc
+--- ceph-15.2.4/src/erasure-code/shec/ErasureCodeShec.cc	2020-07-01 01:10:51.000000000 +0930
++++ ceph-15.2.4-fix_ErasureCodeShec/src/erasure-code/shec/ErasureCodeShec.cc	2020-11-14 00:46:20.029488684 +1030
+@@ -197,7 +197,10 @@
+   }
+   unsigned int k = get_data_chunk_count();
+   unsigned int m = get_chunk_count() - k;
+-  unsigned blocksize = (*chunks.begin()).second.length();
++  unsigned blocksize = 0;
++  if (chunks.size() > 0) {
++    blocksize = (*chunks.begin()).second.length();
++  }
+   for (unsigned int i =  0; i < k + m; i++) {
+     if (chunks.find(i) == chunks.end()) {
+       bufferlist tmp;