fix: additional checks to forbid inline of null consts (#1828)

jadx-core/src/main/java/jadx/core/dex/visitors/ConstInlineVisitor.java

@@ -125,17 +125,30 @@ public class ConstInlineVisitor extends AbstractVisitor {
 		int k = 0;
 		for (RegisterArg useArg : useList) {
 			InsnNode insn = useArg.getParentInsn();
-			if (insn == null) {
-				continue;
-			}
-			if (!canUseNull(insn, useArg)) {
-				useArg.add(AFlag.DONT_INLINE_CONST);
+			if (insn != null && forbidNullArgInline(insn, useArg)) {
 				k++;
 			}
 		}
 		return k == useList.size();
 	}
 
+	private static boolean forbidNullArgInline(InsnNode insn, RegisterArg useArg) {
+		switch (insn.getType()) {
+			case MOVE:
+			case CAST:
+			case CHECK_CAST:
+				// result is null, chain checks
+				return forbidNullInlines(insn.getResult().getSVar());
+
+			default:
+				if (!canUseNull(insn, useArg)) {
+					useArg.add(AFlag.DONT_INLINE_CONST);
+					return true;
+				}
+				return false;
+		}
+	}
+
 	private static boolean canUseNull(InsnNode insn, RegisterArg useArg) {
 		switch (insn.getType()) {
 			case INVOKE:

jadx-core/src/test/java/jadx/tests/integration/others/TestNullInline.java

@@ -0,0 +1,43 @@
+package jadx.tests.integration.others;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.IntegrationTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestNullInline extends IntegrationTest {
+
+	@SuppressWarnings({ "RedundantCast", "DataFlowIssue", "unused" })
+	public static class TestCls {
+		public static Long test(Double d1) {
+			T1<T2, Byte> t1 = (T1<T2, Byte>) null;
+			return t1.t2.l;
+		}
+
+		static class T2 {
+			public long l;
+		}
+
+		static class T1<H, P extends Byte> {
+			public T2 t2;
+
+			public T1(T2 t2) {
+				this.t2 = t2;
+			}
+		}
+	}
+
+	@Test
+	public void test() {
+		assertThat(getClassNode(TestCls.class))
+				.code()
+				.containsOne("Long.valueOf(t1.t2.l);");
+	}
+
+	@Test
+	public void testNoDebug() {
+		noDebugInfo();
+		getClassNode(TestCls.class);
+	}
+}