Ignore invalid instructions

This could be a bad idea, but
it's unclear how to properly
handle these cases.

Resolves #55

src/analysis/slices.rs

@@ -266,8 +266,13 @@ impl FunctionSlices {
                 }
             }
             StepResult::Illegal => {
-                log::debug!("Illegal instruction @ {:#010X}", ins_addr);
+                if ins.code == 0 {
+                    log::debug!("Hit zeroed padding @ {:#010X}", ins_addr);
                     Ok(ExecCbResult::End(false))
+                } else {
+                    log::debug!("Illegal instruction @ {:#010X}", ins_addr);
+                    Ok(ExecCbResult::Continue)
+                }
             }
             StepResult::Jump(target) => match target {
                 BranchTarget::Unknown

src/analysis/tracker.rs

@@ -348,12 +348,15 @@ impl Tracker {
                 }
                 Ok(ExecCbResult::Continue)
             }
-            StepResult::Illegal => bail!(
+            StepResult::Illegal => {
+                log::debug!(
                     "Illegal instruction hit @ {:#010X} (function {:#010X}-{:#010X})",
                     ins_addr,
                     function_start,
                     function_end
-            ),
+                );
+                Ok(ExecCbResult::Continue)
+            }
             StepResult::Jump(target) => match target {
                 BranchTarget::Unknown
                 | BranchTarget::Return