merge NPE bugfix from v0.2

diff --cc nuget-server/src/jetbrains/buildServer/nuget/server/exec/SourcePackageInfo.java
index 51862e114562c1a0aaf52c8fa65ee0c4ef59bc04,0b318ff1d69df0d856f0331c70817e6ef2bd6917..5ab83963b15f38a384c2b1f9a007c7fa1f9d77d7
--- 1/nuget-server/src/jetbrains/buildServer/nuget/server/exec/SourcePackageInfo.java
--- 2/nuget-server/src/jetbrains/buildServer/nuget/server/exec/PackageInfo.java
+++ b/nuget-server/src/jetbrains/buildServer/nuget/server/exec/SourcePackageInfo.java
@@@ -28,7 -28,7 +28,8 @@@ public class SourcePackageInfo 
    private final String myPackageId;\r
    private final String myVersion;\r
  \r
 -  public PackageInfo(@Nullable final String source,\r
++
 +  public SourcePackageInfo(@Nullable final String source,\r
                             @NotNull final String packageId,\r
                             @NotNull final String version) {\r
      mySource = source;\r

diff --cc nuget-server/src/jetbrains/buildServer/nuget/server/trigger/NamedPackagesUpdateChecker.java
index 110c8146651003bed89599a99647889d8719bdb5,85bad5aba13bfea2e6945baec7c29910c567902a..ffbdfe6139b1ea31d5e74705cd17acce04136875
--- 1/nuget-server/src/jetbrains/buildServer/nuget/server/trigger/NamedPackagesUpdateChecker.java
--- 2/nuget-server/src/jetbrains/buildServer/nuget/server/trigger/NamedPackagesUpdateChecker.java
+++ b/nuget-server/src/jetbrains/buildServer/nuget/server/trigger/NamedPackagesUpdateChecker.java
@@@ -61,12 -61,14 +61,14 @@@ public class NamedPackagesUpdateChecke
      return null;\r
    }\r
  \r
 -  private String serializeHashcode(@NotNull final Collection<PackageInfo> _packages) {\r
 -    List<PackageInfo> sorted = new ArrayList<PackageInfo>(_packages);\r
 -    Collections.sort(sorted, new Comparator<PackageInfo>() {\r
 -      public int compare(PackageInfo o1, PackageInfo o2) {\r
 +  private String serializeHashcode(@NotNull final Collection<SourcePackageInfo> _packages) {\r
 +    List<SourcePackageInfo> sorted = new ArrayList<SourcePackageInfo>(_packages);\r
 +    Collections.sort(sorted, new Comparator<SourcePackageInfo>() {\r
 +      public int compare(SourcePackageInfo o1, SourcePackageInfo o2) {\r
          int i;\r
-         if (0 != (i = o1.getSource().compareTo(o2.getSource()))) return i;\r
+         String s1 = o1.getSource();\r
+         String s2 = o2.getSource();\r
+         if (s1 != null && s2 != null && 0 != (i = s1.compareTo(s2))) return i;\r
          if (0 != (i = o1.getPackageId().compareTo(o2.getPackageId()))) return i;\r
          if (0 != (i = o1.getVersion().compareTo(o2.getVersion()))) return i;\r
          return 0;\r