Fix NPE in generics, probably because interface method don't have code

resources/bytecode/javFiles/Bug293.jav

@@ -0,0 +1,13 @@
+import java.lang.Integer;
+import java.lang.Float;
+
+public class Bug293 {
+    bar(a) {
+        return 2 * a;
+    }
+}
+
+interface IFoo {
+    void ga();
+}
+

src/main/java/de/dhbwstuttgart/target/generate/GenerateGenerics.java

@@ -753,7 +753,9 @@ public abstract class GenerateGenerics {
         }
         doIterationForMethods(classOrInterface);
         for (var method : classOrInterface.getMethods()) {
-            referenced.addAll(usedTPHsOfMethods.get(method));
+            var usedTPHs = usedTPHsOfMethods.get(method);
+            if (usedTPHs != null)
+                referenced.addAll(usedTPHs);
         }
         eliminateInnerTypeVariables(referenced, input);
     }

src/test/java/TestComplete.java

@@ -933,4 +933,11 @@ public class TestComplete {
         var clazz = classFiles.get("Bug290A");
         var instance = clazz.getDeclaredConstructor().newInstance();
     }
+
+    @Test
+    public void testBug293() throws Exception {
+        var classFiles = generateClassFiles(new ByteArrayClassLoader(), "Bug293.jav");
+        var clazz = classFiles.get("Bug293");
+        var instance = clazz.getDeclaredConstructor().newInstance();
+    }
 }