Test:type alias merged w/interface-namespace errors

Previously it crashed when it assumed valueDeclaration was always
defined.

tests/baselines/reference/noSymbolForMergeCrash.errors.txt

@@ -0,0 +1,12 @@
+tests/cases/compiler/final.ts(1,6): error TS2649: Cannot augment module 'A' with value exports because it resolves to a non-module entity.
+
+
+==== tests/cases/compiler/initial.ts (0 errors) ====
+    interface A { }
+    namespace A {}
+    
+==== tests/cases/compiler/final.ts (1 errors) ====
+    type A = {}
+         ~
+!!! error TS2649: Cannot augment module 'A' with value exports because it resolves to a non-module entity.
+    

tests/baselines/reference/noSymbolForMergeCrash.js

@@ -0,0 +1,12 @@
+//// [tests/cases/compiler/noSymbolForMergeCrash.ts] ////
+
+//// [initial.ts]
+interface A { }
+namespace A {}
+
+//// [final.ts]
+type A = {}
+
+
+//// [initial.js]
+//// [final.js]

tests/cases/compiler/noSymbolForMergeCrash.ts

@@ -0,0 +1,6 @@
+// @Filename: initial.ts
+interface A { }
+namespace A {}
+
+// @Filename: final.ts
+type A = {}