[PodSourceInstaller] Handle nil values in file patterns

lib/cocoapods/installer/pod_source_installer.rb

@@ -269,6 +269,7 @@ module Pod
       #         specifications (according to their platform) of this Pod.
       #
       def used_files
+
         files = [
           file_accessors.map(&:source_files),
           file_accessors.map(&:resources).map(&:values).flatten,
@@ -277,7 +278,8 @@ module Pod
           file_accessors.map(&:readme),
           file_accessors.map(&:license),
         ]
-        files.flatten.map!{ |path| path.to_s }.uniq
+
+        files.flatten.compact.map{ |path| path.to_s }.uniq
       end
 
       #-----------------------------------------------------------------------#

spec/unit/installer/pod_source_installer_spec.rb

@@ -213,6 +213,17 @@ module Pod
         ]
       end
 
+      it "compacts the used files as nil would be converted to the empty string" do
+        Sandbox::FileAccessor.any_instance.stubs(:source_files)
+        Sandbox::FileAccessor.any_instance.stubs(:resources).returns({})
+        Sandbox::FileAccessor.any_instance.stubs(:preserve_paths)
+        Sandbox::FileAccessor.any_instance.stubs(:prefix_header)
+        Sandbox::FileAccessor.any_instance.stubs(:readme)
+        Sandbox::FileAccessor.any_instance.stubs(:license)
+        paths = @installer.send(:used_files)
+        paths.should == []
+      end
+
     end
 
     #-------------------------------------------------------------------------#