Fix "ANDROID_HOME environment variable is not set correctly" error

Fixes NativeScript/nativescript-cli#1242

Author: Fatme Havaluova

helpers.ts

@@ -25,6 +25,10 @@ function cmdQuote(s: string): string {
 }
 
 export function quoteString(s: string): string {
+	if (!s) {
+		return s;
+	}
+
 	return (platform() === "win32") ? cmdQuote(s) : bashQuote(s);
 }
 

test/unit-tests/sys-info-base.ts

@@ -227,6 +227,22 @@ describe("sysInfoBase", () => {
 				};
 			});
 
+			describe("when android info is incorrect", () => {
+				it("pathToAdb and pathToAndroid are null", () => {
+					childProcessResult.adbVersion = {
+						result: null
+					};
+					childProcessResult.androidInstalled = {
+						result: false
+					};
+					testInjector = createTestInjector(childProcessResult, {isWindows: false, isDarwin: false, dotNetVersion: "4.5.1"}, null);
+					sysInfoBase = testInjector.resolve("sysInfoBase");
+					let result = sysInfoBase.getSysInfo(toolsPackageJson, {pathToAdb: null, pathToAndroid: null}).wait();
+					assert.deepEqual(result.adbVer, null);
+					assert.deepEqual(result.androidInstalled, false);
+				});
+			});
+
 			describe("when all of calls throw", () => {
 				let assertAllValuesAreNull = () => {
 					sysInfoBase = testInjector.resolve("sysInfoBase");