Fix small angle check when ACC is disabled or not defined

Fixes related to #9185

src/main/flight/imu.c

@@ -724,5 +724,9 @@ void imuQuaternionHeadfreeTransformVectorEarthToBody(t_fp_vector_def *v)
 
 bool isUpright(void)
 {
-    return attitudeIsEstablished && getCosTiltAngle() > smallAngleCosZ;
+#ifdef USE_ACC
+    return !sensors(SENSOR_ACC) || (attitudeIsEstablished && getCosTiltAngle() > smallAngleCosZ);
+#else
+    return true;
+#endif
 }

src/test/unit/flight_imu_unittest.cc

@@ -234,8 +234,7 @@ uint16_t disableFlightMode(flightModeFlags_e mask)
 
 bool sensors(uint32_t mask)
 {
-    UNUSED(mask);
-    return false;
+    return mask & SENSOR_ACC;
 };
 
 uint32_t millis(void) { return 0; }