NPE when trying to build a maven module that has no src folder
```
[ERROR] Failed to execute goal io.quarkus:quarkus-maven-plugin:0.19.1:build (default) on project behavior-definition: Failed to build a runnable JAR: Failed to build a runner jar: NullPointerException -> [Help 1]
```

Error handling should be improved here.

Cause: the module had no src folder structure defined
diff --git a/core/creator/src/main/java/io/quarkus/creator/phase/augment/AugmentPhase.java b/core/creator/src/main/java/io/quarkus/creator/phase/augment/AugmentPhase.java
index ebef51df795..13531a254fb 100644
--- a/core/creator/src/main/java/io/quarkus/creator/phase/augment/AugmentPhase.java
+++ b/core/creator/src/main/java/io/quarkus/creator/phase/augment/AugmentPhase.java
@@ -208,10 +208,19 @@ public void provideOutcome(AppCreator ctx) throws AppCreatorException {
         }
         if (!Files.exists(appClassesDir)) {
             final Path appJar = appState.getAppArtifact().getPath();
-            try {
-                ZipUtils.unzip(appJar, appClassesDir);
-            } catch (IOException e) {
-                throw new AppCreatorException("Failed to unzip " + appJar, e);
+            //manage project without src directory
+            if (appJar == null) {
+                try {
+                    Files.createDirectory(appClassesDir);
+                } catch (IOException e) {
+                    throw new AppCreatorException("Failed to create classes directory " + appClassesDir, e);
+                }
+            } else {
+                try {
+                    ZipUtils.unzip(appJar, appClassesDir);
+                } catch (IOException e) {
+                    throw new AppCreatorException("Failed to unzip " + appJar, e);
+                }
             }
             final Path metaInf = appClassesDir.resolve(META_INF);
             IoUtils.recursiveDelete(metaInf.resolve("maven"));
['core/creator/src/main/java/io/quarkus/creator/phase/augment/AugmentPhase.java']