fix array access out of bounds

static variable buf does not allow reentrance here (would be better put on stack = not static)

git-svn-id: https://openmodelica.org/svn/OpenModelica/trunk@11091 f25d12d1-65f4-0310-ae8a-bbce733d8d8e

Compiler/runtime/System_omc.cpp

@@ -680,7 +680,7 @@ extern const char* System_snprintff(const char *fmt, int len, double d)
   static char buf[1024];
   assert(1024>len);
   snprintf(buf,len,fmt,d);
-  buf[1024] = 0;
+  buf[1023] = 0;
 }
 
 }