fix an issue when input showing error message the layout would change

SessionUIKit/Components/SessionTextField.swift

@@ -56,12 +56,18 @@ public struct SessionTextField: View {
                 .stroke(themeColor: (error?.isEmpty == false) ? .danger : .borderSeparator)
             )
             
-            Text(error ?? " ")
+            ZStack {
+                Text(error ?? "")
                     .bold()
                     .font(.system(size: Values.mediumFontSize))
                     .foregroundColor(themeColor: .danger)
                     .multilineTextAlignment(.center)
             }
+            .frame(
+                height: 50,
+                alignment: .top
+            )
+        }
     }
 }