Better exception display: read value in ValueException

Author: yuxiaomao

src/HLAdapter.hx

@@ -469,6 +469,15 @@ class HLAdapter extends DebugSession {
 			var exc = dbg.getException();
 			var str = null;
 			if( exc != null ) {
+				switch( exc.t ) {
+				case HObj({ name:"haxe.ValueException" }):
+					try {
+						exc = dbg.eval.readField(exc, "value");
+					} catch(e) {
+						debug("Error extracting ValueException value: " + e.message);
+					}
+				default:
+				}
 				str = switch( exc.v ) {
 				case VString(str, _): str;
 				default: dbg.eval.valueStr(exc);