From: Jeroen Demeyer
Allow error recovery. See discussion at
http://trac.sagemath.org/ticket/20710#comment:18

diff --git a/src/env/error.c b/src/env/error.c
index a898b76..154de0f 100644
--- a/src/env/error.c
+++ b/src/env/error.c
@@ -50,6 +50,7 @@ static void errfunc(const char *fmt, ...)
       va_end(arg);
       xprintf("Error detected in file %s at line %d\n",
          env->err_file, env->err_line);
+      env->err_st = 0;
       if (env->err_hook != NULL)
          env->err_hook(env->err_info);
       abort();
