Correct initialization of convergence loop

src/AMBER/background.py

@@ -613,11 +613,10 @@ class background():
 
         # Loss function
         loss = []#np.zeros(n_epochs, dtype=self.dtype)
-        old_loss = 2000000
-        new_loss = 1000000
+        old_loss = 0
+        new_loss = 0
         k = 0
-
-        while (old_loss - new_loss > 1e-3) and (k < n_epochs):
+        while ((old_loss - new_loss > 1e-3) and (k < n_epochs)) or k < 2:
             # Compute A = Y - B by filling the nans with 0s
             A = np.where(np.isnan(Y_r - b_tmp) == True, 0.0, Y_r - b_tmp)