Handle errors in package.json gracefully

spec/atom-spec.coffee

@@ -19,6 +19,10 @@ describe "the `atom` global", ->
           expect(object.data).toBe 5
           expect(pack.activateStylesheets).toHaveBeenCalled()
 
+        it "continues if the package fails to load", ->
+          config.set("core.disabledPackages", [])
+          expect(-> atom.loadPackage("package-that-throws-on-load")).not.toThrow()
+
     describe ".unloadPackage(name)", ->
       describe "when the package is active", ->
         it "throws an error", ->

spec/fixtures/packages/package-that-throws-on-load/package.json

@@ -0,0 +1 @@
+INVALID

spec/spec-helper.coffee

@@ -63,7 +63,7 @@ beforeEach ->
   config.set "editor.fontFamily", "Courier"
   config.set "editor.fontSize", 16
   config.set "editor.autoIndent", false
-  config.set "core.disabledPackages", ["package-that-throws-an-exception"]
+  config.set "core.disabledPackages", ["package-that-throws-an-exception", "package-that-throws-on-load"]
   config.save.reset()
   atom.config = config
   window.config = config

src/package-manager.coffee

@@ -66,8 +66,9 @@ class PackageManager
 
     if packagePath = @resolvePackagePath(name)
       return pack if pack = @getLoadedPackage(name)
+
       pack = Package.load(packagePath, options)
-      if pack.metadata.theme
+      if pack.metadata?.theme
         atom.themes.register(pack)
       else
         @loadedPackages[pack.name] = pack