When displaying multispans, ignore empty lines adjacent to ...
```
error[E0308]: `match` arms have incompatible types
--> tests/ui/codemap_tests/huge_multispan_highlight.rs:98:18
|
6 | let _ = match true {
| ---------- `match` arms have incompatible types
7 | true => (
| _________________-
8 | | // last line shown in multispan header
... |
96 | |
97 | | ),
| |_________- this is found to be of type `()`
98 | false => "
| __________________^
... |
119 | |
120 | | ",
| |_________^ expected `()`, found `&str`
error[E0308]: `match` arms have incompatible types
--> tests/ui/codemap_tests/huge_multispan_highlight.rs:215:18
|
122 | let _ = match true {
| ---------- `match` arms have incompatible types
123 | true => (
| _________________-
124 | |
125 | | 1 // last line shown in multispan header
... |
213 | |
214 | | ),
| |_________- this is found to be of type `{integer}`
215 | false => "
| __________________^
216 | |
217 | |
218 | | 1 last line shown in multispan
... |
237 | |
238 | | ",
| |_________^ expected integer, found `&str`
```
