fix: panic on empty ump text iterator

Author: Ben Leadbetter

src/ump_stream/endpoint_name.rs

@@ -97,4 +97,14 @@ mod tests {
         let message = EndpointName::try_from(&buffer[..]).unwrap();
         assert_eq!(message.name(), "Gimme some signal 🔊 🙌");
     }
+
+    #[test]
+    fn read_empty_bytes() {
+        assert_eq!(
+            EndpointName::<std::vec::Vec<u32>>::new()
+                .name_bytes()
+                .collect::<std::vec::Vec<u8>>(),
+            std::vec![]
+        );
+    }
 }

src/ump_stream/function_block_name.rs

@@ -190,4 +190,14 @@ mod tests {
             0x9,
         );
     }
+
+    #[test]
+    fn read_empty_bytes() {
+        assert_eq!(
+            FunctionBlockName::<std::vec::Vec<u32>>::new()
+                .name_bytes()
+                .collect::<std::vec::Vec<u8>>(),
+            std::vec![],
+        );
+    }
 }

src/ump_stream/mod.rs

@@ -268,14 +268,14 @@ pub struct TextBytesIterator<'a> {
 impl<'a> core::iter::Iterator for TextBytesIterator<'a> {
     type Item = u8;
     fn next(&mut self) -> Option<Self::Item> {
+        while !self.finished() && self.value() == 0 {
+            self.advance();
+        }
         if self.finished() {
             return None;
         }
         let ret = Some(self.value());
         self.advance();
-        while !self.finished() && self.value() == 0 {
-            self.advance();
-        }
         ret
     }