vbscript: Return after assert(0) to silence warnings.

dlls/vbscript/compile.c

@@ -1400,6 +1400,7 @@ static HRESULT create_class_funcprop(compile_ctx_t *ctx, function_decl_t *func_d
             break;
         default:
             assert(0);
+            return E_FAIL;
         }
 
         assert(!desc->entries[invoke_type]);

dlls/vbscript/global.c

@@ -1012,6 +1012,7 @@ static HRESULT Global_InStr(vbdisp_t *This, VARIANT *args, unsigned args_cnt, VA
         return E_NOTIMPL;
     default:
         assert(0);
+        return E_FAIL;
     }
 
     if(startv) {