Resolve "Solveur: Les select d'une session chargée ne s'initialise pas"

Closes #668 (closed), #669 (closed)

src/styles.scss

@@ -33,6 +33,10 @@ button {
     to { transform: translateX(400%); } */
 }
 
+.mat-error {
+    font-size: 14px !important;
+    font-weight: 500 !important;
+}
 // --------- bootstrap inspired styles ---------
 
 h1 {