gen_isr_tables: Add meaningful error message

When using direct isrs, a vector table is needed. However, if none is
present , i.e. `CONFIG_GEN_IRQ_VECTOR_TABLE=n`, this script failed. The
given error message was not helpful (`'NoneType' has no len()`).
This change makes it clearer, where to look for the problem.

Signed-off-by: Greter Raffael <[email protected]>

Author: raffi-g

scripts/build/gen_isr_tables.py

@@ -358,6 +358,10 @@ def main():
 
     for irq, flags, func, param in intlist["interrupts"]:
         if flags & ISR_FLAG_DIRECT:
+            if not vt:
+                error("Direct Interrupt %d declared with parameter 0x%x "
+                      "but no vector table in use"
+                      % (irq, param))
             if param != 0:
                 error("Direct irq %d declared, but has non-NULL parameter"
                         % irq)