797: plugin inspection null pointer exception

Author: Iamwade

src/com/magento/idea/magento2plugin/inspections/xml/PluginDeclarationInspection.java

@@ -9,10 +9,7 @@
 import com.intellij.codeInspection.ProblemsHolder;
 import com.intellij.ide.highlighter.XmlFileType;
 import com.intellij.openapi.util.Pair;
-import com.intellij.psi.PsiElement;
-import com.intellij.psi.PsiElementVisitor;
-import com.intellij.psi.PsiFile;
-import com.intellij.psi.XmlElementVisitor;
+import com.intellij.psi.*;
 import com.intellij.psi.search.GlobalSearchScope;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.psi.xml.XmlAttribute;
@@ -175,6 +172,11 @@ private List<Pair<String, String>> fetchModuleNamesWhereSamePluginNameUsed(
                     final PsiFile file
             ) {
                 final List<Pair<String, String>> modulesName = new ArrayList<>();
+                final PsiDirectory parentDirectory = file.getContainingDirectory();
+
+                if (parentDirectory == null) {
+                    return modulesName;
+                }
                 final String currentFileDirectory = file.getContainingDirectory().toString();
                 final String currentFileFullPath =
                         currentFileDirectory.concat(File.separator).concat(file.getName());