don't report missing constructors if superclass has none

langserver/java/validation/missing-constructor.js

@@ -18,12 +18,14 @@ function checkConstructor(source_type, probs) {
         // - which means the inherited class is Object (and a default constructor exists)
         return;
     }
+    if (superclass.constructors.length) {
         if (!superclass.constructors.find(c => c.parameterCount === 0)) {
             // the source type has no declared constructors, but the superclass
             // does not include a default (parameterless) constructor
             probs.push(ParseProblem.Error(source_type.nameToken, `Class '${source_type.fullyDottedRawName}' requires a constructor to be declared because the inherited class '${superclass.fullyDottedRawName}' does not define a default constructor.`));
         }
     }
+}
 
 /**
  * @param {SourceType[]} source_types