Fix multiple issues regarding sources loading too late

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -40,6 +40,7 @@ import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
 import com.google.android.material.elevation.SurfaceColors
 import com.google.android.material.transition.platform.MaterialContainerTransform
 import dev.chrisbanes.insetter.applyInsetter
+import eu.kanade.core.util.ifSourcesLoaded
 import eu.kanade.domain.base.BasePreferences
 import eu.kanade.presentation.reader.DisplayRefreshHost
 import eu.kanade.presentation.reader.OrientationSelectDialog
@@ -344,6 +345,10 @@ class ReaderActivity : BaseActivity() {
                 )
             }
 
+            if (!ifSourcesLoaded()) {
+                return@setComposeContent
+            }
+
             val isHttpSource = viewModel.getSource() is HttpSource
             val isFullscreen by readerPreferences.fullscreen().collectAsState()
             val flashOnPageChange by readerPreferences.flashOnPageChange().collectAsState()

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderViewModel.kt

@@ -47,6 +47,7 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.filterNotNull
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
@@ -264,6 +265,7 @@ class ReaderViewModel @JvmOverloads constructor(
             try {
                 val manga = getManga.await(mangaId)
                 if (manga != null) {
+                    sourceManager.isInitialized.first { it }
                     mutableState.update { it.copy(manga = manga) }
                     if (chapterId == -1L) chapterId = initialChapterId