Fix flow errors

Author: tharakawj

Diff for: packages/react-error-overlay/src/containers/CompileErrorContainer.js

@@ -33,7 +33,9 @@ class CompileErrorContainer extends PureComponent<Props, void> {
       <ErrorOverlay>
         <Header headerText="Failed to compile" />
         <a
-          onClick={canOpenInEditor ? () => editorHandler(errLoc) : null}
+          onClick={
+            canOpenInEditor && errLoc ? () => editorHandler(errLoc) : null
+          }
           style={canOpenInEditor ? codeAnchorStyle : null}
         >
           <CodeBlock main={true} codeHTML={generateAnsiHTML(error)} />

Diff for: packages/react-error-overlay/src/index.js

@@ -29,7 +29,7 @@ let iframe: null | HTMLIFrameElement = null;
 let isLoadingIframe: boolean = false;
 var isIframeReady: boolean = false;
 
-let editorHandler: null | OpenInEditorListener = null;
+let editorHandler: null | EditorHandler = null;
 let currentBuildError: null | string = null;
 let currentRuntimeErrorRecords: Array<ErrorRecord> = [];
 let currentRuntimeErrorOptions: null | RuntimeReportingOptions = null;