fix: use findByName for signing config to support F-Droid builds

Author: DevonStee

app/build.gradle.kts

@@ -60,9 +60,10 @@ android {
         }
         release {
             isMinifyEnabled = true
-            val releaseConfig = signingConfigs.getByName("release")
-            if (releaseConfig.storeFile != null) {
-                signingConfig = releaseConfig
+            signingConfigs.findByName("release")?.let { releaseConfig ->
+                if (releaseConfig.storeFile != null) {
+                    signingConfig = releaseConfig
+                }
             }
         }
     }