Another fix in debug trace.

engine/vm.c

@@ -1733,6 +1733,7 @@ PH7_PRIVATE sxi32 VmExtractDebugTrace(ph7_vm *pVm, SySet *pDebugTrace) {
 					break;
 				}
 			}
+			if(aTrace.pFile) {
 				aTrace.pClassName = NULL;
 				aTrace.bThis = FALSE;
 				if(pFunc->iFlags & VM_FUNC_CLASS_METHOD) {
@@ -1751,6 +1752,7 @@ PH7_PRIVATE sxi32 VmExtractDebugTrace(ph7_vm *pVm, SySet *pDebugTrace) {
 					break;
 				}
 			}
+		}
 		/* Roll frame */
 		pVm->pFrame = pVm->pFrame->pParent;
 	}