Address some OkHttp nullability issues

app/src/main/java/eu/kanade/tachiyomi/data/cache/PagePreviewCache.kt

@@ -169,12 +169,12 @@ class PagePreviewCache(private val context: Context) {
             editor = diskCache.edit(key) ?: throw IOException("Unable to edit key")
 
             // Get OutputStream and write page with Okio.
-            response.body!!.source().saveTo(editor.newOutputStream(0))
+            response.body.source().saveTo(editor.newOutputStream(0))
 
             diskCache.flush()
             editor.commit()
         } finally {
-            response.body?.close()
+            response.body.close()
             editor?.abortUnlessCommitted()
         }
     }

app/src/main/java/eu/kanade/tachiyomi/source/online/all/EHentai.kt

@@ -1087,7 +1087,7 @@ class EHentai(
                     .url(EH_API_BASE)
                     .post(json.toString().toRequestBody(JSON))
                     .build(),
-            ).execute().body!!.string(),
+            ).execute().body.string(),
         )
 
         val obj = outJson["tokenlist"]!!.jsonArray.first().jsonObject
@@ -1216,7 +1216,7 @@ class EHentai(
                 if (response.isSuccessful) {
                     val body = ByteArrayOutputStream()
                         .use {
-                            val bitmap = BitmapFactory.decodeStream(response.body!!.byteStream())
+                            val bitmap = BitmapFactory.decodeStream(response.body.byteStream())
                                 ?: throw IOException("Null bitmap($thumbnailPreview)")
                             Bitmap.createBitmap(
                                 bitmap,

app/src/main/java/eu/kanade/tachiyomi/source/online/all/NHentai.kt

@@ -62,7 +62,7 @@ class NHentai(delegate: HttpSource, val context: Context) :
     }
 
     override suspend fun parseIntoMetadata(metadata: NHentaiSearchMetadata, input: Response) {
-        val json = GALLERY_JSON_REGEX.find(input.body?.string().orEmpty())!!.groupValues[1].replace(
+        val json = GALLERY_JSON_REGEX.find(input.body.string())!!.groupValues[1].replace(
             UNICODE_ESCAPE_REGEX,
         ) { it.groupValues[1].toInt(radix = 16).toChar().toString() }
         val jsonResponse = jsonParser.decodeFromString<JsonResponse>(json)