fix: `getFormat` get wrong format when `BlockEmbed` in range

[demo](https://quilljs.com/playground/snow#codeN4Ig9AlgdgJgpgDwHQAsAuBbANiAXCAHgCMBXNNAeygAIIYBeAHRCLSmYD4BzONagMwoAnDAEM0BMKXJUOjKARgQAbrQbM4SykM6SlyuewUBnAMZCIABz7GhppuGjxkAK2O6wZi9Y4gANI6wiEhueCCmVMZ8AI4kEFhY1PTUUHAA7tQAinEJABQA5ADEmhDa+X7UwPLU1BgUMCRYcMa4ldU11JQUWESiQq0A2u0d1APA1ChwovD9owCMFQBMFfyiWMZwALrUAL6bfsMdA-lE3TDl1PnKdHAUF-mlaxCm9yRBQljQcPn7hzXHEDEPHuEXgAFoiFgKKYANY-A40Dq-RE7BE1SxYUSmOAoM5wWb5ADCFAwlgoG2oohocEszyQ9PK7TQkwwcFa+WMUAoaQuYDA1GEl1IREh33kOwAlABueTyWLxLBIDZoYlQNBwNXGXJDRE1Kq6kbUZjiNAWaTNZitfWGm1GlhnS2dIQkOB-Dqot01ZjQDZCNCO5hzRYAZiDweYhw9Buttu9UF9-rwdsYspAkbRHRjNrjCcdWdtXpA13gFADIHVUSQEQwEYNIx26cO+ZGxvIZrIFqTzdj9qwMEdppdnt2GezIB9+MTrUDIbDtfro7adY6OcnZZT7DTBobUE2EtlUFYUCQVFMn1hSWouQlSQ4S5q8oSSt4AGU4E1TGgIFRcgAGCpzAALPuiIRPG3RwEgUJcLkj6KjwaAAGLCGIaB-gBwEgTsIA7EAA) The case in demo, format should return `{ blod: true }` but get `{}`. This is because `BlockEmbed` is included in the calculation of blot. But `BlockEmbed` doesn't have attributes, make the intersection attribute empty.