[Coverity 1398436] Use after free in svg.c

This could cause an immediate crash or incorrect values might be read subsequently resulting in incorrect computations.

In svg_LoadTemplate: A pointer to freed memory is dereferenced, used as a function argument, or otherwise used (CWE-416)

123    if( psz_template )
124    {
      CID 1398415:String not null terminated (STRING_NULL) [ "select issue" ]
125        p_sys->psz_token = strstr( psz_template, SVG_TEMPLATE_BODY_TOKEN );
      9. Condition !p_sys->psz_token, taking true branch.
126        if( !p_sys->psz_token )
127        {
128            msg_Err( p_filter, "'%s' not found in SVG template", SVG_TEMPLATE_BODY_TOKEN );
      10. freed_arg: free frees psz_template.
129            free( psz_template );
      11. Falling through to end of if statement.
130        }
131        else *((char*)p_sys->psz_token) = 0;
132    }
133
     
CID 1398436: (#1 of 1): Use after free (USE_AFTER_FREE)
12. use_after_free: Using freed pointer psz_template.
134    p_sys->psz_file_template = psz_template;