Update src/sage/quadratic_forms/quadratic_form.py

Co-authored-by: Travis Scrimshaw <[email protected]>

Author: fchapoton

src/sage/quadratic_forms/quadratic_form.py

@@ -579,11 +579,7 @@ def __init__(self, R, n=None, entries=None, unsafe_initialization=False, number_
         elif is_Polynomial(R) or is_MPolynomial(R):
             p = R
 
-            if p.is_zero():
-                pass
-            elif p.is_homogeneous() and p.degree() == 2:
-                pass
-            else:
+            if not p.is_zero() and not (p.is_homogeneous() and p.degree() == 2):
                 raise ValueError("polynomial is neither zero nor homogeneous of degree 2")
 
             P = p.parent()