Fix a bad slice into erroring utf-8 buffer (#872)

crates/nu-command/src/strings/str_/collect.rs

@@ -42,11 +42,18 @@ impl Command for StrCollect {
         // let output = input.collect_string(&separator.unwrap_or_default(), &config)?;
         // Hmm, not sure what we actually want. If you don't use debug_string, Date comes out as human readable
         // which feels funny
-        #[allow(clippy::needless_collect)]
-        let strings: Vec<String> = input
-            .into_iter()
-            .map(|value| value.debug_string("\n", &config))
-            .collect();
+        let mut strings: Vec<String> = vec![];
+
+        for value in input {
+            match value {
+                Value::Error { error } => {
+                    return Err(error);
+                }
+                value => {
+                    strings.push(value.debug_string("\n", &config));
+                }
+            }
+        }
 
         let output = if let Some(separator) = separator {
             strings.join(&separator)