6990209: JCK7-compiler lang/ICLS/icls006/icls00603/icls00603a.html#icls00603src test fails.

Reviewed-by: jjg

src/share/classes/com/sun/tools/javac/tree/TreeInfo.java

@@ -502,7 +502,7 @@ public class TreeInfo {
                 else super.visitVarDef(that);
             }
             public void visitTypeParameter(JCTypeParameter that) {
-                if (that.type.tsym == sym) result = that;
+                if (that.type != null && that.type.tsym == sym) result = that;
                 else super.visitTypeParameter(that);
             }
         }