Revises isSingleFloat32Struct

isSingleFloat32Struct currently stops when the current handle is not a
value class handle, or it has more than one field.

If not, it proceeds to the next step with the assumption that the current.

Unfortunately, if the current handle is not a value class, but has one
field (somehow), getFieldInClass call raises an assertion failure
discussed in #6569.

This commit tries to fix this invalid terminating condition.

Author: parjong

src/jit/compiler.cpp

@@ -475,7 +475,7 @@ bool Compiler::isSingleFloat32Struct(CORINFO_CLASS_HANDLE clsHnd)
     for (;;)
     {
         // all of class chain must be of value type and must have only one field
-        if (!info.compCompHnd->isValueClass(clsHnd) && info.compCompHnd->getClassNumInstanceFields(clsHnd) != 1)
+        if (!info.compCompHnd->isValueClass(clsHnd) || info.compCompHnd->getClassNumInstanceFields(clsHnd) != 1)
         {
             return false;
         }