Check for null confidence string.

git-svn-id: http://google-refine.googlecode.com/svn/trunk@259 7d457c2a-affb-35e4-300a-418c747d4874

src/main/java/com/metaweb/gridworks/ProjectMetadata.java

@@ -166,8 +166,10 @@ public class ProjectMetadata implements Jsonizable {
     }
     
     public void setEncodingConfidence(String confidence) {
+    	if (confidence != null) {
     		this.setEncodingConfidence(Integer.parseInt(confidence));
     	}
+    }
 
     public int getEncodingConfidence() {
         return _encodingConfidence;