fix edge case in F8->u8

src/lib.rs

@@ -61,7 +61,11 @@ impl From<F8> for u8 {
 			return 0;
 		}
 		let (m, e) = value.split_unbias();
-		if e >= 0 { m << e } else { m >> -e }
+		match e {
+			0.. => m << e,
+			-7..0 => m >> -e,
+			..-7 => 0,
+		}
 	}
 }