Fix LSP semantic coloration bailing out sometimes

Step to reproduce:

```
xx := Window {
   TouchArea {
      clicked => {
         if (true) {}
         // note: because there is no else, the semantic colouring is bailing out now
      }
   }
   TouchArea { clicked => {} }
}
```

This is caused by a bug in rowan::SyntaxToken::next_token that doesn't visit
the next token if it has an empty node

Unfortunately, the LSP has no tests, so I couldn't add one easily

internal/compiler/parser.rs

@@ -693,6 +693,31 @@ impl SyntaxToken {
     pub fn parent(&self) -> SyntaxNode {
         SyntaxNode { node: self.token.parent().unwrap(), source_file: self.source_file.clone() }
     }
+    pub fn next_token(&self) -> Option<SyntaxToken> {
+        // Due to a bug (as of rowan 0.15.3), rowan::SyntaxToken::next_token doesn't work if a
+        // sibling don't have tokens.
+        // For example, if we have an expression like  `if (true) {}`  the
+        // ConditionalExpression has an empty Expression/CodeBlock  for the else part,
+        // and next_token doesn't go into that.
+        // So re-implement
+
+        let token = self
+            .token
+            .next_sibling_or_token()
+            .and_then(|e| match e {
+                rowan::NodeOrToken::Node(n) => n.first_token(),
+                rowan::NodeOrToken::Token(t) => Some(t),
+            })
+            .or_else(|| {
+                self.token.ancestors().find_map(|it| it.next_sibling_or_token()).and_then(|e| {
+                    match e {
+                        rowan::NodeOrToken::Node(n) => n.first_token(),
+                        rowan::NodeOrToken::Token(t) => Some(t),
+                    }
+                })
+            })?;
+        Some(SyntaxToken { token, source_file: self.source_file.clone() })
+    }
 }
 
 impl std::fmt::Display for SyntaxToken {
@@ -745,6 +770,11 @@ impl SyntaxNode {
     pub fn parent(&self) -> Option<SyntaxNode> {
         self.node.parent().map(|node| SyntaxNode { node, source_file: self.source_file.clone() })
     }
+    pub fn first_token(&self) -> Option<SyntaxToken> {
+        self.node
+            .first_token()
+            .map(|token| SyntaxToken { token, source_file: self.source_file.clone() })
+    }
 }
 
 #[derive(Debug, Clone, derive_more::From)]