Fixed source of null pointer exception

Author: halirutan

resources/META-INF/plugin.xml

@@ -2,7 +2,7 @@
   <id>de.halirutan.mathematica</id>
   <name>Mathematica Support</name>
   <category>Custom Language</category>
-  <version>2.0.10</version>
+  <version>2.0.11</version>
   <idea-version since-build="163.7743.44"/>
   <vendor email="patrick@halirutan.de" url="http://mathematicaplugin.halirutan.de">Patrick Scheibe</vendor>
   <depends>com.intellij.modules.lang</depends>

src/de/halirutan/mathematica/codeinsight/highlighting/MathematicaHighlightingAnnotator.java

@@ -150,7 +150,7 @@ public void visitStringifiedSymbol(final StringifiedSymbol stringifiedSymbol) {
   public void visitMessageName(final MessageName messageName) {
     final StringifiedSymbol tag = messageName.getTag();
     TextAttributesKey color = MathematicaSyntaxHighlighterColors.MESSAGE;
-    if ("usage".equals(tag.getText())) {
+    if (tag != null && "usage".equals(tag.getText())) {
       color = MathematicaSyntaxHighlighterColors.USAGE_MESSAGE;
     }
     final ASTNode[] children = messageName.getNode().getChildren(null);