diff --git a/ms2/src/org/labkey/ms2/pipeline/mascot/MascotClientImpl.java b/ms2/src/org/labkey/ms2/pipeline/mascot/MascotClientImpl.java
index 6266fda745..12266a8e24 100644
--- a/ms2/src/org/labkey/ms2/pipeline/mascot/MascotClientImpl.java
+++ b/ms2/src/org/labkey/ms2/pipeline/mascot/MascotClientImpl.java
@@ -92,7 +92,7 @@ public MascotClientImpl(String url, Logger instanceLogger)
 
     public MascotClientImpl(String url, Logger instanceLogger, String userAccount, String userPassword)
     {
-        _url = url;
+        _url = (null == url) ? "" : url;
         _instanceLogger = (null == instanceLogger) ? _log : instanceLogger;
         _userAccount = (null == userAccount) ? "" : userAccount;
         _userPassword = (null == userPassword) ? "" : userPassword;
diff --git a/nab/src/org/labkey/nab/NabAssayController.java b/nab/src/org/labkey/nab/NabAssayController.java
index 3dc834a349..e380e01072 100644
--- a/nab/src/org/labkey/nab/NabAssayController.java
+++ b/nab/src/org/labkey/nab/NabAssayController.java
@@ -201,7 +201,7 @@ protected DilutionAssayProvider getProvider(ExpRun run)
     {
         AssayProvider provider = AssayService.get().getProvider(run.getProtocol());
         if (!(provider instanceof DilutionAssayProvider))
-            throw new IllegalArgumentException("Run " + run.getRowId() + " is not a NAb run.");
+            throw new NotFoundException("Run " + run.getRowId() + " is not a NAb run.");
         return (DilutionAssayProvider) provider;
     }