handle case when there is no input after escape

src/utils/read_until.rs

@@ -31,6 +31,7 @@ pub(crate) fn read_until_open_curly_brace<I: Iterator<Item = Token>>(
                 if toks.peek().is_some() {
                     t.push(toks.next().unwrap());
                 }
+                continue;
             }
             _ => {}
         }

tests/if.rs

@@ -122,3 +122,7 @@ error!(
     condition_is_evaluated_eagerly,
     "@if 1 + 1 =s {\n}", "Error: expected \"=\"."
 );
+error!(
+    nothing_after_escape,
+    "@if \\", "Error: Expected expression."
+);