Fix NPE Exception in ReplaceLambdaWithMethodReference

Author: tkvangorder

rewrite-java/src/main/java/org/openrewrite/java/cleanup/RenamePrivateFieldsToCamelCase.java

@@ -97,14 +97,19 @@ public JavaSourceFile visitJavaSourceFile(JavaSourceFile cu, ExecutionContext ct
         public J.VariableDeclarations.NamedVariable visitVariable(J.VariableDeclarations.NamedVariable variable, ExecutionContext ctx) {
             Cursor parentScope = getCursorToParentScope(getCursor());
 
-            // Does support renaming private fields in a J.ClassDeclaration.
-            if ((parentScope.getParent() != null && parentScope.getParent().getValue() instanceof J.ClassDeclaration && variable.getVariableType().hasFlags(Flag.Private) &&
-                    //do not rename constants
-                    !(variable.getVariableType().hasFlags(Flag.Static, Flag.Final)) &&
-                    // Does not apply for instance variables of inner classes
-                    !((J.ClassDeclaration) parentScope.getParent().getValue()).getType().getFullyQualifiedName().contains("$") &&
-                    // Name does not match camelCase pattern.
-                    !LOWER_CAMEL.matches(variable.getSimpleName()))) {
+            // Does support renaming fields in a J.ClassDeclaration.
+            // We must have a variable type to make safe changes.
+            // Only make changes to private fields that are not constants.
+            // Does not apply for instance variables of inner classes
+            // Only make a change if the variable does not conform to lower camelcase format.
+            if (parentScope.getParent() != null
+                    && parentScope.getParent().getValue() instanceof J.ClassDeclaration
+                    && variable.getVariableType() != null
+                    && variable.getVariableType().hasFlags(Flag.Private)
+                    && !(variable.getVariableType().hasFlags(Flag.Static, Flag.Final))
+                    && !((J.ClassDeclaration) parentScope.getParent().getValue()).getType().getFullyQualifiedName().contains("$")
+                    && !LOWER_CAMEL.matches(variable.getSimpleName())) {
+
                 String toName = LOWER_CAMEL.format(variable.getSimpleName());
                 ((Map<J.VariableDeclarations.NamedVariable, String>) getCursor().getNearestMessage("RENAME_VARIABLES_KEY")).put(variable, toName);
             } else {