CSSDocument: add null check for tokenStream
diff --git a/compiler/src/main/java/org/apache/royale/compiler/internal/css/CSSDocument.java b/compiler/src/main/java/org/apache/royale/compiler/internal/css/CSSDocument.java
index 96d0beb..978df55 100644
--- a/compiler/src/main/java/org/apache/royale/compiler/internal/css/CSSDocument.java
+++ b/compiler/src/main/java/org/apache/royale/compiler/internal/css/CSSDocument.java
@@ -178,7 +178,10 @@
         setColumn(column);
         setEndLine(endLine);
         setEndColumn(endColumn);
-        setSourcePath(tokenStream.getSourceName());
+        if (tokenStream != null)
+        {
+            setSourcePath(tokenStream.getSourceName());
+        }
     }
 
     private final ImmutableList<ICSSRule> rules;