Set custom amount on focus, do not clear on loss of focus.

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/subscription/boost/BoostFragment.kt

@@ -200,7 +200,9 @@ class BoostFragment : DSLSettingsBottomSheetFragment(
               viewModel.setCustomAmount(it)
             },
             onCustomAmountFocusChanged = {
-              viewModel.setCustomAmountFocused(it)
+              if (it) {
+                viewModel.setCustomAmountFocused()
+              }
             }
           )
         )

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/subscription/boost/BoostViewModel.kt

@@ -217,8 +217,8 @@ class BoostViewModel(
     store.update { it.copy(customAmount = FiatMoney(bigDecimalAmount, it.customAmount.currency)) }
   }
 
-  fun setCustomAmountFocused(isFocused: Boolean) {
-    store.update { it.copy(isCustomAmountFocused = isFocused) }
+  fun setCustomAmountFocused() {
+    store.update { it.copy(isCustomAmountFocused = true) }
   }
 
   private data class BoostInfo(val boosts: List<Boost>, val defaultBoost: Boost?, val boostBadge: Badge, val supportedCurrencies: Set<Currency>)