fix(test): Add back test for inject with invalid span

The previous commit replaced the invalid-span inject test with a
no-span-in-context test. These are distinct scenarios: an explicitly
invalid span vs no span at all. Restore the invalid span test and
keep both.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: adinauer

sentry-opentelemetry/sentry-opentelemetry-otlp/src/test/kotlin/OtelSentryPropagatorTest.kt

@@ -172,7 +172,7 @@ class OpenTelemetryOtlpPropagatorTest {
   }
 
   @Test
-  fun `does not inject headers if span is invalid`() {
+  fun `does not inject headers when no span in context`() {
     val propagator = OpenTelemetryOtlpPropagator()
     val carrier = mutableMapOf<String, String>()
 
@@ -182,6 +182,17 @@ class OpenTelemetryOtlpPropagatorTest {
     assertNull(carrier["baggage"])
   }
 
+  @Test
+  fun `does not inject headers when span is invalid`() {
+    val propagator = OpenTelemetryOtlpPropagator()
+    val carrier = mutableMapOf<String, String>()
+
+    propagator.inject(Context.root().with(Span.getInvalid()), carrier, MapSetter())
+
+    assertNull(carrier["sentry-trace"])
+    assertNull(carrier["baggage"])
+  }
+
   @Test
   fun `does not inject baggage header when baggage is missing from context`() {
     val propagator = OpenTelemetryOtlpPropagator()