Better handling of exceptions during loading

If we get an exception during load, don't define half of window.Olm (which
confuses apps).

This is a partial fix to https://github.com/vector-im/riot-web/issues/2726.

javascript/olm_post.js

@@ -419,4 +419,22 @@ olm_exports["get_library_version"] = restore_stack(function() {
         getValue(buf+2, 'i8'),
     ];
 });
-}();
+
+})();
+
+// export the olm functions into the environment.
+//
+// make sure that we do this *after* populating olm_exports, so that we don't
+// get a half-built window.Olm if there is an exception.
+
+if (typeof module !== 'undefined' && module.exports) {
+    // node / browserify
+    module.exports = olm_exports;
+}
+
+if (typeof(window) !== 'undefined') {
+    // We've been imported directly into a browser. Define the global 'Olm' object.
+    // (we do this even if module.exports was defined, because it's useful to have
+    // Olm in the global scope for browserified and webpacked apps.)
+    window["Olm"] = olm_exports;
+}

javascript/olm_pre.js

@@ -2,32 +2,24 @@ var olm_exports = {};
 var get_random_values;
 var process; // Shadow the process object so that emscripten won't get
              // confused by browserify
-if (typeof(global) !== 'undefined' && global["window"]) {
-    // We're running with browserify
-    module["exports"] = olm_exports;
-    global["window"]["Olm"] = olm_exports;
-    get_random_values = function(buf) {
-        window.crypto.getRandomValues(buf);
-    };
-} else if (typeof(window) !== 'undefined') {
-    // We've been imported directly into a browser.
-    window["Olm"] = olm_exports;
+
+if (typeof(window) !== 'undefined') {
+    // We've in a browser (directly, via browserify, or via webpack).
     get_random_values = function(buf) {
         window.crypto.getRandomValues(buf);
     };
 } else if (module["exports"]) {
     // We're running in node.
-    module["exports"] = olm_exports;
     var nodeCrypto = require("crypto");
     get_random_values = function(buf) {
         var bytes = nodeCrypto.randomBytes(buf.length);
         buf.set(bytes);
-    }
+    };
     process = global["process"];
 } else {
     throw new Error("Cannot find global to attach library to");
 }
 
-var init = function() {
+(function() {
     var module; // Shadow the Node 'module' object so that emscripten won't try
                 // to fiddle with it.