Safer completion handling for callfuncs.

Fixes #352

src/Program.spec.ts

@@ -1826,6 +1826,21 @@ describe('Program', () => {
             }
         });
 
+        it('does not crash on callfunc operator', () => {
+            //there needs to be at least one xml component WITHOUT an interface
+            program.addOrReplaceFile<XmlFile>('components/MyNode.xml', trim`<?xml version="1.0" encoding="utf-8" ?>
+                <component name="Component1" extends="Scene">
+                    <script type="text/brightscript" uri="pkg:/components/MyNode.bs" />
+                </component>
+            `);
+            const file = program.addOrReplaceFile('source/main.bs', `
+                sub main()
+                    someFunc()@.
+                end sub
+            `);
+            program.getCompletions(file.pathAbsolute, util.createPosition(2, 32));
+        });
+
         it('gets signature help for constructor with no args', () => {
             program.addOrReplaceFile('source/main.bs', `
                 function main()

src/Program.ts

@@ -654,7 +654,8 @@ export class Program {
         let funcNames = new Set<string>();
         let currentScope = scope;
         while (isXmlScope(currentScope)) {
-            for (let name of currentScope.xmlFile.ast.component.api.functions.map((f) => f.name)) {
+            const functionNames = currentScope.xmlFile.ast.component.api?.functions.map((f) => f.name) ?? [];
+            for (let name of functionNames) {
                 if (!filterName || name === filterName) {
                     funcNames.add(name);
                 }