replaced split_line with a multibyte aware version

split_line was working fine as long as the input was just plain US-ASCII. When using multibyte characters and they happened to be at the end of the line to spit the function did panic.

The new code returns correctly split lines even if they contain multibyte characters.

src/generator/ical.rs

@@ -19,13 +19,13 @@ fn get_value(value: &Option<String>) -> String {
 }
 
 pub(crate) fn split_line<T: Into<String>>(str: T) -> String {
-    let mut str = str.into();
-    let mut x = 75;
-    while x < str.len() {
-        str.insert_str(x, "\r\n ");
-        x += 77;
-    }
-    str
+    let str = str.into();
+    let mut chars = str.chars();
+    let sub_string = (0..)
+        .map(|_| chars.by_ref().take(75).collect::<String>())
+        .take_while(|s| !s.is_empty())
+        .collect::<Vec<_>>();
+    sub_string.join("\r\n ")
 }
 
 //